Optical recording method, optical recorder, and optical recording medium

ABSTRACT

The object of the present invention is to provide an optical recording method for recording data in an optical recording medium, which can reduce jitter of a reproduced signal even in the case where data are recorded at a plurality of linear recording velocities.  
     The optical recording method according to the present invention can record data at a plurality of linear recording velocities or a continuously changing linear recording velocity and a recording waveform for modulating a recording beam includes a direct current section and a recording pulse section. Data are recorded so that the intensity Pbi of the direct current section and the intensity Pw of the recording pulse section satisfy PbiH/PbiL&lt;1 and (PbiH/PwH)/(PbiL/PwL)&lt;1 where PwL and PbiL are Pw and Pbi when data are to be recorded at a linear recording velocity V L  and PwH and PbiH are Pw and Pbi when data are to be recorded at a linear recording velocity V H  higher than the linear recording velocity V L  and satisfying 1.1≦V H /V L . As a result, it is possible to reduce jitter of a reproduced signal even in the case where data are recorded over a wide range of linear velocities.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an optical recording medium, amethod for recording data in the same and an apparatus for recordingdata in the same and, particularly, to a phase change type opticalrecording medium, a method for recording data in the same and anapparatus for recording data in the same.

DESCRIPTION OF THE PRIOR ART

[0002] Recently, optical recording media in which data can be recordedwith high density and from which recorded data can be erased haveattracted attention. Among phase change type optical recording mediadata, the rewritable type optical recording media are recorded with databy projecting a laser beam onto a recording layer, thereby changing thecrystalline state thereof, and data are reproduced by detecting changein the reflection coefficients of the recording layer due to the phasechange. The phase change type optical recording medium has attractedattention because data recorded in the phase change type opticalrecording medium can be overwritten by modulating the power of a singlelaser beam and the optical system of a driving apparatus can besimplified in comparison with that for optical magnetic recording media.

[0003] In the phase change type optical recording medium in which datacan be overwritten, an amorphous record mark is formed by irradiating acrystalline recording layer with a laser beam having a recording powerlevel, melting it and quickly cooling the melted recording layer. Whendata are to be erased in the phase change type optical recording medium,the amorphous record mark is crystallized by irradiating the recordmark, heating it to a temperature equal to or higher than thecrystallizing temperature and lower than the melting point thereof, andgradually cooling it.

[0004] Illustrative examples of the practical optical recording media inwhich data can be overwritten include the CD-RW, DVD-RW and DVD-RAM. TheCD-RW has the substantially same capacity of 640 MB as that of the CD-DA(compact disk). In the CD-RW, data are practically recorded at a linearvelocity of four to ten times that of the CD-DA. On the other hand, inthe DVD-RW and DVD-RAM, each having the same capacity of 4.7 GB as thatof a DVD-ROM, data are usually recorded at 1× linear velocity (originallinear velocity) and are not practically recorded at a linear velocityexceeding that double the original linear velocity. This is because therecording density of the DVD-RW and DVD-RAM is extremely high incomparison with that of the CD-RW and it is difficult to overwrite dataover a wide range of linear velocities while maintaining jitter low. Inthe case of recording data at a higher density than that of the DVD(Digital Versatile Disk) system media, it is further difficult tooverwrite data over a wide range of linear velocities while maintainingjitter low.

[0005] It is therefore an object of the present invention to provide anoptical recording method for recording data in an optical recordingmedium, which can reduce jitter of a reproduced signal even in the casewhere data are recorded over a wide range of linear velocities.

[0006] Further, it is another object of the present invention toprovided an optical recording apparatus for recording data in an opticalrecording medium, which can reduce jitter of a reproduced signal even inthe case where data are recorded over a wide range of linear velocities.

[0007] Moreover, it is a further object of the present invention toprovide an optical recording medium which can reduce jitter of areproduced signal even in the case where data are recorded over a widerange of linear velocities.

DISCLOSURE OF THE PRESENT INVENTION

[0008] The above objects of the present invention can be accomplished by(1) to (24) below.

[0009] (1) An optical recording method for recording data in an opticalrecording medium having a recording layer containing a phase changematerial at a plurality of linear recording velocities or a continuouslychanging linear recording velocity using a recording beam whoseintensity is modulated in accordance with a recording waveform,

[0010] the recording waveform including a direct current section havingan intensity of Pbi and a recording pulse section for forming a recordmark, the recording pulse section including at least three upwardpulses, among which an upward pulse between a first upward pulse and alast upward pulse has an intensity of Pw, Pbi and Pw being set so as tosatisfy PbiH/PbiL<1 and (PbiH/PwH)/(PbiL/PwL)<1 where PbiL and PwL arePbi and Pw when data are to be recorded at a linear recording velocityV_(L) selected from among the plurality of linear recording velocitiesor the continuously changing linear recording velocity and PbiH and PwHare Pbi and Pw when data are to be recorded at a linear recordingvelocity V_(H) which satisfies 1.1≦V_(H)/V_(L).

[0011] (2) An optical recording method for recording data in an opticalrecording medium having a recording layer containing a phase changematerial at a linear recording velocity selected from among a pluralityof linear recording velocities using a recording beam whose intensity ismodulated in accordance with a recording waveform,

[0012] the recording waveform including a direct current section havingan intensity of Pbi and a recording pulse section for forming a recordmark, the recording pulse section including at least three upwardpulses, among which an upward pulse between a first upward pulse and alast upward pulse has an intensity of Pw, Pbi and Pw being set so as tosatisfy PhiH/PbiL<1 and (PbiH/PwH)/(PbiL/PwL)<1 where PbiL and PwL arePhi and Pw when data are to be recorded at a linear recording velocityV_(L) and PbiH and PwH are Pbi and Pw when data are to be recorded at alinear recording velocity V_(H) which satisfies 1.1≦V_(H)/V_(L).

[0013] (3) An optical recording method for recording data in an opticalrecording medium defined in (1) or (2), wherein the recording pulsesection further includes a downward pulse having a width of Tcl andfollowing the last upward pulse and TclL and TclH are set so as tosatisfy TclH/TclL<1 where TclL is Tcl when data are to be recorded atthe linear recording velocity V_(L) and TclH is Tcl when data are to berecorded at the linear recording velocity V_(H).

[0014] (4) An optical recording method for recording data in an opticalrecording medium defined in any one of (1) to (3), wherein the upwardpulse between the first upward pulse and the last upward pulse has awidth Tmp, and TmpL and TmpH are set so as to satisfy TmpH/TmpL≦1 whereTmpL is Tmp when data are to be recorded at the linear recordingvelocity V_(L) and TmpH is Tmp when data are to be recorded at thelinear recording velocity V_(H).

[0015] (5) An optical recording method for recording data in an opticalrecording medium defined in any one of (1) to (4), wherein the firstupward pulse has a width of Ttop, and TtopL and TtopH are set so as tosatisfy TtopH/TtopL≦1 where TtopL is Ttop when data are to be recordedat the linear recording velocity V_(L) and TtopH is Ttop when data areto be recorded at the linear recording velocity V_(H).

[0016] (6) An optical recording method for recording data in an opticalrecording medium defined in any one of (1) to (5), wherein the lastupward pulse has a width of Tlp, and TlpL and TlpH are set so as tosatisfy 1≦TlpH/TlpL where TlpL is Tlp when data are to be recorded atthe linear recording velocity V_(L) and TlpH is Tlp when data are to berecorded at the linear recording velocity V_(H).

[0017] (7) An optical recording method for recording data in an opticalrecording medium defined in any one of (1) to (6), wherein theintensities of the pulses and the widths of the pulses used at therespective linear recording velocities V_(L) and V_(H) are determined bytest recording.

[0018] (8) An optical recording method for recording data in an opticalrecording medium defined in any one of (1) to (6), wherein n·Tw≦20 ns issatisfied at a highest linear recording velocity where Tw is a width ofa detection window and n·Tw is a signal length corresponding to ashortest record mark.

[0019] (9) An optical recording method for recording data in an opticalrecording medium having a recording layer containing a phase changematerial using a recording beam whose intensity is modulated inaccordance with a recording waveform, the recording waveform including adirect current section having an intensity of Pbi and a recording pulsesection for forming a record mark, the recording pulse section includingat least three upward pulses, among which an upward pulse between afirst upward pulse and a last upward pulse has an intensity of Pw, areference linear recording velocity and recommended values of Pw and Pbiwhen data are to be recorded at the reference linear recording velocitybeing given, and PbiL, which is Pbi when data are to be recorded at alinear recording velocity V_(L), and PbiH, which is Pbi when data are tobe recorded at a linear recording velocity V_(H), being set so as tosatisfy PbiH/PbiL<1 and (PbiH/PwH)/(PbiL/PwL)<1 where one of the linearrecording velocity V_(L) and the linear recording velocity V_(H) is thereference linear recording velocity and the other thereof is a linearrecording velocity used for test recording, the linear recordingvelocity V_(L) and the linear recording velocity V_(H) satisfy1.1≦V_(H)/V_(L), thereby determining Pw and Pbi used for the testrecording or when data are to be recorded at a linear recording velocityregion including the linear recording velocity for the test recording.

[0020] (10) An optical recording method for recording data in an opticalrecording medium defined in (9), wherein the recording pulse sectionfurther includes a downward pulse following the last upward pulse andhaving a width of Tcl, a recommended value of Tcl when data are to berecorded at the reference linear recording velocity is given, and Tclfor the test recording is set so as to satisfy TclH/TclL<1 where TclL isTcl when data are to be recorded at the linear recording velocity V_(L)and TclH is Tcl when data are to be recorded at the linear recordingvelocity V_(H), thereby determining Tcl used for the test recording orwhen data are to be recorded at a linear recording velocity regionincluding the linear recording velocity for the test recording.

[0021] (11) An optical recording method for recording data in an opticalrecording medium defined in (9) or (10), wherein the upward pulsebetween the first upward pulse and the last upward pulse has a widthTmp, a recommended value of Tmp at the reference linear recordingvelocity is given, and Tmp for the test recording is set so as tosatisfy TmpH/TmpL≦1 where TmpL is Tmp when data are to be recorded atthe linear recording velocity V_(L) and TmpH is Tmp when data are to berecorded at the linear recording velocity V_(H), thereby determining Tmpused for the test recording or when data are to be recorded at a linearrecording velocity region including the linear recording velocity forthe test recording.

[0022] (12) An optical recording method for recording data in an opticalrecording medium defined in any one of (9) to (11), wherein the firstpulse has a width Ttop, a recommended value of Ttop at the referencelinear recording velocity is given, and Ttop for the test recording isset so as to satisfy TtopH/TtopL≦1 where TtopL is Ttop when data are tobe recorded at the linear recording velocity V_(L) and TtopH is Ttopwhen data are to be recorded at the linear recording velocity V_(H),thereby determining Ttop used for the test recording or when data are tobe recorded at a linear recording velocity region including the linearrecording velocity for the test recording.

[0023] (13) An optical recording method for recording data in an opticalrecording medium defined in any one of (9) to (12), wherein the lastpulse has a width Tlp, a recommended value of Tlp at the referencelinear recording velocity is given, and Tlp for the test recording isset so as to satisfy 1≦TlpH/TlpL where TlpL is Tlp when data are to berecorded at the linear recording velocity V_(L) and TlpH is Tlp whendata are to be recorded at the linear recording velocity V_(H), therebydetermining Tlp used for the test recording or when data are to berecorded at a linear recording velocity region including the linearrecording velocity for the test recording.

[0024] (14) An optical recording method for recording data in an opticalrecording medium defined in any one of (9) to (13), wherein n·Tw≦20 nsis satisfied at a highest linear recording velocity where Tw is a widthof a detection window and n·Tw is a signal length corresponding to ashortest record mark.

[0025] (15) An optical recording apparatus for recording data in anoptical recording medium in accordance with the optical recording methoddefined in any one of (1) to (8), the optical recording apparatus beingconstituted so as to store pulse intensities and pulse widths used atthe linear recording velocity V_(L) and the linear recording velocityV_(H).

[0026] (16) An optical recording apparatus for recording data in anoptical recording medium in accordance with the optical recording methoddefined in any one of (1) to (8), the optical recording apparatus beingconstituted so as to store a plurality of pulse intensities and aplurality of pulse widths used at each of the linear recording velocityV_(L) and the linear recording velocity V_(H) and select a pulseintensity and a pulse width used for recording data in the opticalrecording medium from the plurality of pulse intensities and theplurality of pulse widths by test recording of data in the opticalrecording medium.

[0027] (17) An optical recording apparatus for recording data in anoptical recording medium in accordance with the optical recording methoddefined in any one of (1) to (8), pulse intensities and pulse widthsused at the linear recording velocity V_(L) and the linear recordingvelocity V_(H) being defined as functions of the linear recordingvelocity V_(L) and the linear recording velocity V_(H) and the opticalrecording apparatus being constituted so as to store the functions.

[0028] (18) An optical recording apparatus for recording data in anoptical recording medium in accordance with the optical recording methoddefined in any one of (1) to (8), pulse intensities and pulse widthsused at the linear recording velocity V_(L) and the linear recordingvelocity V_(H) being defined as functions of the linear recordingvelocity V_(L) and the linear recording velocity V_(H) and the opticalrecording apparatus being constituted so as to store a plurality of thefunctions for each of the linear recording velocity V_(L) and the linearrecording velocity V_(H) and select functions used for recording data inthe optical recording medium from the plurality of the functions by testrecording of data in the optical recording medium.

[0029] (19) An optical recording apparatus for recording data in anoptical recording medium in accordance with the optical recording methoddefined in any one of (9) to (14), the optical recording apparatus beingconstituted so as to store recommended values of the pulse intensity andthe pulse width used at the reference linear recording velocity.

[0030] (20) An optical recording medium in which data are to be recordedin accordance with the optical recording method defined in any one of(1) to (8), the optical recording medium being constituted so as tostore pulse intensities and pulse widths used at the linear recordingvelocity V_(L) and the linear recording velocity V_(H).

[0031] (21) An optical recording medium in which data are to be recordedin accordance with the optical recording method defined in any one of(1) to (8), the optical recording medium being constituted so as tostore a plurality of pulse intensities and a plurality of pulse widthsused at each of the linear recording velocity V_(L) and the linearrecording velocity V_(H) and so that a pulse intensity and a pulse widthused for recording data in the optical recording medium are selectedfrom among the plurality of pulse intensities and the plurality of pulsewidths by test recording of data in the optical recording medium.

[0032] (22) An optical recording medium in which data are to be recordedin accordance with the optical recording method defined in any one of(1) to (8), pulse intensities and pulse widths used at the linearrecording velocity V_(L) and the linear recording velocity V_(H) beingdefined as functions of the linear recording velocity V_(L) and thelinear recording velocity V_(H) and the optical recording medium beingconstituted so as to store the functions.

[0033] (23) An optical recording medium in which data are to be recordedin accordance with the optical recording method defined in any one of(1) to (8), pulse intensities and pulse widths used at the linearrecording velocity V_(L) and the linear recording velocity V_(H) beingdefined as functions of the linear recording velocity V_(L) and thelinear recording velocity V_(H) and the optical recording medium beingconstituted so as to store a plurality of the functions for each of thelinear recording velocity V_(L) and the linear recording velocity V_(H)and so that functions used for recording data in the optical recordingmedium are selected from among the plurality of the functions by testrecording of data in the optical recording medium.

[0034] (24) An optical recording medium in which data are to be recordedin accordance with the optical recording method defined in any one of(9) to (14), the optical recording medium being constituted so as tostore recommended values of the pulse intensity and the pulse width atthe reference linear recording velocity.

[0035] The above objects of the present invention can be alsoaccomplished by an optical recording method for recording data in anoptical recording medium having a recording layer containing a phasechange material by irradiating it with a recording beam whose intensityis modulated between a plurality of power levels including at least arecording power and a bias power, a recording power PwL and a bias powerPbiL when data are to be recorded at a first linear recording velocityand a recording power PwH and a bias power PbiH when data are to berecorded at a second linear recording velocity higher than the firstlinear recording velocity being set so as to satisfy PbiH/PbiL<1 and(PbiH/PwH)/(PbiL/PwL)<1.

[0036] According to the present invention, jitter of a reproduced signalcan be reduced even when data are recorded at a wide range of linearrecording velocities.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037]FIG. 1 is a graph showing a 5T signal and a recording waveformthereof.

[0038]FIG. 2 is a graph showing a recording waveform of a 4T signal.

[0039]FIG. 3 is a graph showing a recording waveform of a 3T signal.

[0040]FIG. 4 is a drawing showing a write strategy when data are to berecorded using the (1, 7) RLL modulation code wherein FIG. 4(a) is adrawing showing a write strategy for forming a 3T signal, FIG. 4(b) is adrawing showing a write strategy for forming a 4T signal, FIG. 4(c) is adrawing showing a write strategy for forming a 5T signal and FIG. 4(d)is a drawing showing a write strategy for forming a 5T signal to a 8Tsignal.

[0041]FIG. 5 is a cross sectional view showing one configuration of anoptical recording medium.

[0042]FIG. 6 is a cross sectional view showing another configuration ofan optical recording medium.

[0043]FIG. 7 is a block diagram schematically showing a primary portionof an optical recording apparatus 50 for recording data in an opticalrecording medium shown in FIG. 5 or 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] Hereinafter, a preferred embodiment of the present invention willbe described in detail referring to the accompany drawings.

[0045] Data are recorded in an optical recording medium by irradiatingthe optical recording medium with a recording beam and forming a numberof record marks, and the length between the starting point and theterminal point of an individual record mark and the length between theterminal point of the record mark and the starting point of a nextrecording mark constitute data. The length of each record mark and thelength between neighboring record marks (edges) are determined to be alength corresponding to one among 3T to 11T and 14T where T is the cycleof a clock in the case where the EPM plus (8-16) modulation code, whichis sometimes called the 8-16 modulation code, is employed and they aredetermined to be a length corresponding to one among 2T to 8T in thecase where the (1, 7) RLL modulation code, which is sometimes called the1-7 modulation code is employed.

[0046] When data are to be recorded in a phase change type opticalrecording medium, it is general to perform multi-pulse recording as setout in Japanese Patent Application Laid-Open Nos. 10-106008, 11-232652and 2000-155945 without direct-currently projecting a recording beamcorrespondingly to the length of a record mark.

[0047]FIG. 1 shows a recording waveform used for the multi-pulserecording. A recording waveform as termed in this specification meansthe pattern of a drive signal for modulating the power of a recordingbeam. A 5T signal of an NRZI signal in the case where the EPM plus(8-16) modulation code is employed and the recording waveformcorresponding to the 5T signal are shown in FIG. 1.

[0048] In FIG. 1, the symbol Pw designates recording power, the symbolPbi designates bias power and the symbol Pho designates bottom power.Pbi is usually called the erasing power in a system capable ofoverwriting data. The recording waveform includes a recording pulsesection for forming a record mark and a direct current section forerasing a record mark. The recording pulse section has a configurationof repeating an upward pulse having a recording power Pw and a followingdownward pulse having a bottom power Pbo, and the entire recording pulsesection is raised from Phi and returned to Pbi. Therefore, theneighboring recording pulse sections are connected via the directcurrent section.

[0049] In FIG. 1, the symbol Ttop designates the width of a first upwardpulse and the symbol Tmp designates the width of an upward pulse betweenthe first upward pulse and the last upward pulse, which is sometimescalled a multi-pulse. the symbol Tlp designates the width of the lastupward pulse and the symbol Tcl designates the width of a downward pulseadded to the end of the last pulse, which is sometimes called a coolingpulse. These pulse widths are expressed as values normalized with areference clock width (1T). In the recording waveform shown in FIG. 1,the power of all of the downward pulses including the cooling pulse,namely, the bottom power Pbo, are set to be lower than the bias powerPbi.

[0050]FIG. 2 shows a recording waveform of a 4T signal in the case wherethe EPM plus (8-16) modulation code is employed. A recording pulsesection in the recording waveform is constituted by two upward pulsesand downward pulses each following one of the upward pulses. In therecording pulse section, the width of a first upward pulse is designatedTtop and the width of the second upward pulse from the beginning isdesignated Tlp.

[0051]FIG. 3 shows a recording waveform of a 3T signal which is theshortest signal in the case where the EPM plus (8-16) modulation code isemployed. A recording pulse section in the recording waveform isconstituted by a single upward pulse and a single downward pulse. In therecording pulse section, the width of the upward pulse is designatedTtop.

[0052] In this manner, in the case where the EPM plus (8-16) modulationcode is employed, the number of upward pulses is determined to be (k□2)where k is a multiple of T and assumes one among 3 to 11 and 14.Therefore, although not shown in Figures, in the case where a 6T to 11Tor 14T signal is formed, the number of upward pulses is equal to 4 to 9or 12. All upward pulses between the first upward pulse and the lastupward pulse are multi-pulses and in the case where a 6T to 11T or 14Tsignal is formed, the number of the multi-pulses is equal to 2 to 7 or10.

[0053] In this specification, each of the pulse widths is normalizedwith the reference clock width. In the case where the modulation code isnot changed even if the linear recording velocity is changed, since thereference clock width is changed inversely to the linear recordingvelocity, the length of a recording mark of the same signal on themedium is constant irrespective of the linear recording velocity.Therefore, linear recording density, namely, the bit density, isconstant irrespective of the linear recording velocity. For example, ifthe linear recording velocity is reduced to half, the reference pulsewidth is doubled. In this manner, data may be recorded in an opticalrecording medium at a plurality of linear recording velocities. Theoptical recording medium in which data can be recorded at a plurality oflinear recording velocities is sometimes called a multi-speed typeoptical recording medium and data recording in the multi-speed typeoptical recording medium is sometimes called multi-speed recording.

[0054] When data are recorded in an optical recording medium using theCAV (constant angular velocity) format in which the rotational speed iskept constant, the linear recording velocity increases toward the outercircumference of the optical recording medium. Therefore, data arerecorded in the optical recording medium at a continuously changinglinear recording velocity.

[0055] In the present invention, in the case where data are to berecorded in a phase change optical recording medium at a plurality oflinear recording velocities or a continuously changing linear recordingvelocity, the pulse intensity (power level) and the pulse width arecontrolled in accordance with a linear recording velocity in order toreduce jitter of signals reproduced from data recorded at all linearrecording velocity regions in the following manner.

[0056] First, a linear recording velocity V_(L) and a linear recordingvelocity V_(H) which is higher than the linear recording velocity V_(L)are selected from among the plurality of the linear recording velocitiesor the values of the continuously changing recording velocity.Preferably, the linear recording velocity V_(L) and the linear recordingvelocity V_(H) satisfy 1.1≦V_(H)/V_(L).

[0057] Further, in the present invention, in the recording waveformwhose recording pulse section includes at least three upward pulses,data are to be recorded in an optical recording medium so as to satisfyPbiH/PbiL<1 and (PbiH/PwH)/(PbiL/PwL)<1 where the symbols PwL and PbiLare Pw and Pbi when data are to be recorded at the linear recordingvelocity V_(L) and the symbols PwH and PbiH are Pw and Pbi when data arebe recorded at the linear recording velocity V_(H).

[0058] As a result, in the case where data are recorded at high density,jitter can be reduced even if data are recorded at either of the linearrecording velocities V_(L) and V_(H). Namely, in the case where themulti-speed recording is performed or where data are recorded using theCAV format, linear recording jitter can be reduced when data arerecorded at any linear recording velocity. This effect becomes morepronounced as the ratio of V_(H) to V_(L) increases.

[0059] Further, it is preferable to set the value PbiH/PbiL to besmaller and the value (PbiH/PwH)/(PboL/PwL) to be smaller, as the valueV_(H)/V_(L) increases.

[0060] If PwL, PbiL, PwH and PbiH satisfy (PbiH/PwH)/(PbiL/PwL)<1, theynaturally satisfy PbiL/PwL>PbiH/PwH and therefore, they satisfyPwH/PwL>PbiH/PbiL. Namely, in the present invention, although Pbi isdecreased as the linear recording velocity increases, Pw may beincreased, decreased or made constant as the linear recording velocityincreases. However, if Pw is decreased as the linear recording velocityincreases, the reduction ratio of Pw is set to be higher than that ofPbi, whereby jitter can be suppressed within a tolerance over a widerange of linear recording velocities.

[0061] Jitter can be reduced because re-crystallization of the phasechange material is suppressed by setting pulse intensity in this mannerand re-crystallization of the recording layer can be suppressed becausethe influence of thermal interference is lowered by setting pulseintensity in this manner. Although the influence of thermal interferencebecomes great as the linear recording velocity is increased, if pulseintensity is set in the above described manner, the amount of heatapplied to the recording layer when data are recorded at the recordingvelocity is suppressed, thereby suppressing re-crystallization of therecording layer.

[0062] Further, in the present invention, it is preferable to recorddata in an optical recording medium so as to satisfy TclH/TclL<1 whereTclL is Tcl when data are to be recorded at the linear recordingvelocity V_(L) and TclH is Tcl when data are to be recorded at thelinear recording velocity V_(H). As a result, it is possible to preventjitter from increasing due to change in the linear recording velocityover a wide range of linear recording velocities.

[0063] Furthermore, in the present invention, it is preferable to recorddata in an optical recording medium so as to satisfy TmpH/TmpL≦1 whereTmpL is Tmp when data are to be recorded at the linear recordingvelocity V_(L) and TmpH is Tmp when data are to be recorded at thelinear recording velocity V_(H). As a result, it is possible to furtherprevent jitter from increasing due to change in the linear recordingvelocity over a wide range of linear recording velocities.

[0064] Moreover, in the present invention, it is preferable to recorddata in an optical recording medium so as to satisfy TtopH/TtopL≦1 whereTtopL is Ttop when data are to be recorded at the linear recordingvelocity V_(L) and TtopH is Ttop when data are to be recorded at thelinear recording velocity V_(H). As a result, it is possible to furtherprevent jitter from increasing due to change in the linear recordingvelocity over a wide range of linear recording velocities.

[0065] Further, in the present invention, it is preferable to recorddata in an optical recording medium so as to satisfy 1≦TlpH/TlpL,preferably, 1<TlpH/TlpL, where TlpL is Tlp when data are to be recordedat the linear recording velocity V_(L) and TlpH is Tlp when data are tobe recorded at the linear recording velocity V_(H). As a result, it ispossible to further prevent jitter from increasing due to change in thelinear recording velocity over a wide range of linear recordingvelocities.

[0066] In the case of setting pulse widths so as to satisfy TmpH/TmpL≦1and/or TtopH/TtopL≦1, since thermal interference can be reduced andre-crystallization of the recording layer can be suppressed similarly tothe case of setting pulse widths so as to satisfy PbiH/PbiL<1 and(PbiH/PwH)/(PbiL/PwL)<1, jitter can be further prevented fromincreasing.

[0067] On the other hand, in the case of setting pulse widths so as tosatisfy TclH/TclL<1 and/or 1≦TlpH/TlpL, since the efficiency for erasingan existing record mark can be increased, jitter can be furtherprevented from increasing. More specifically, since the setting of Tcland Tlp influences the crystallization of the rear edge region of therecord mark and a region following it (a region between neighboringrecord marks), in the case where a record mark is already formed in thisregion, namely, in the case where this region is in an amorphous phase,the record mark cannot be erased (crystallized) in a desired manner dueto the shortage of heat. Since this tendency becomes pronounced as thelinear recording velocity is increased, it is possible to improve theefficiency for erasing an existing record mark and further preventjitter from increasing by setting pulse widths so as to satisfyTclH/TclL<1 and/or 1≦TlpH/TlpL.

[0068] The pulse intensities and the pulse widths used with therespective linear recording velocities V_(L) and V_(H) are determined sothat PbiH/PbiL, (PbiH/PwH)/(PbiL/PwL), TmpH/TmpL, TclH/TclL, TtopH/TtopLand TlpH/TlpL are within ranges prescribed by the present invention.Information for setting the pulse intensities and the pulse widths usedwith the respective linear recording velocities V_(L) and V_(H) may bestored in an optical recording apparatus or recorded in an opticalrecording medium. Specifically, these values may be tabulated to bestored in a storing means in the optical recording apparatus or to berecorded in advance in the optical recording medium. Further, insteadtabulating these values, it is possible, for example, to define pulseintensities and pulse widths used with the respective recordingvelocities as functions of the linear recording velocity and store thefunctions in the storing means or record them in the optical recordingmedium. Such information is sometimes referred to as “information forsetting recording conditions”.

[0069] The present invention is required to enable recording of data ata plurality of linear recording velocities, namely, of performingmulti-speed recording of data in a CLV (Constant Linear Velocity)format, and the present invention is effective in the case where theplurality of linear recording velocities are greatly different from eachother. In this case, the plurality of linear recording velocities areusually defined as an original linear velocity (3.49 m/s in the DVD-RAM)and integer multiples thereof, but it is not absolutely necessary forthem to include integer multiples of the original linear velocity. Itfurther is not absolutely necessary for them to include the originallinear velocity and the present invention may be applied to a high speeddata recording system in which data can be recorded at only a linearrecording velocity equal to or more than twice the original linearvelocity or a linear recording velocity equal to or more than four timesthe original linear velocity.

[0070] Thus, one of the features of the present invention lies in thatthe relationship between recording conditions at different linearrecording velocities is determined in a data recording system in whichdata can be recorded in the CLV format and at a plurality of linearrecording velocities. Therefore, the present invention includes a casewhere data are to be recorded on one optical recording medium belongingto such a data recording system at a certain linear recording velocityselected from among the plurality of linear recording velocities.

[0071] Another feature of the present invention lies in that therelationship between recording conditions at each of linear recordingvelocities among a continuously changing linear velocity are determinedin a data recording system in which data are to be recorded in the CAV(Constant Angular Velocity). Since data are recorded in a disk-likeoptical recording medium rotating at a constant rotational speed in theCAV format, data are recorded in the optical recording medium at acontinuously changing linear velocity and, therefore, the linearvelocity at the outer circumferential portion of the optical recordingmedium is higher than that at the inner circumferential portion.

[0072] In this specification, the CLV format includes the MCLV (ModifiedCLV) format and the CAV format includes the MCAV (Modified CAV) format.The MCLV format and the MCAV format are referred to in, for example,“Optical Disk Technology,” page 233, published by Radio Technology Co.Ltd. on Feb. 10, 1989.

[0073] In the present invention, even in the case where the linearrecording velocity increases or decreases continuously, it is notnecessary to continuously control the pulse intensities and the pulsewidths. For example, in the case of recording data in the CAV format,although the linear recording velocity continuously changes, it is notnecessary to continuously change the pulse intensities and the pulsewidths so as to correspond to the continuous change in the linearrecording velocity, and several combinations of the pulse intensitiesand the pulse widths may be used. Specifically, it is possible to dividethe linear recording velocity between the lowest linear recordingvelocity and the highest linear recording velocity of the CAV formatinto a plurality of linear recording velocity regions and set onecombination of the pulse intensities and the pulse widths for each ofthe thus divided linear recording velocity regions.

[0074] In the case where data are to be recorded in a disk-like opticalrecording medium in the CAV format, the ratio of the linear recordingvelocity at the most inner circumferential portion thereof to that atthe most outer circumferential portion thereof is generally 2 to 3 andusually 2.5. In this case, the number of combinations of the pulseintensities and the pulse widths to be determined is preferably equal toor larger than 2 and more preferably equal to or larger than 3. If thenumber of the combinations is too few, the advantage of the presentinvention becomes slight. On the other hand, since the effect ofdecreasing jitter is not markedly increased even if the number of thecombinations is increased, it is unnecessary for the number ofcombinations to exceed 40. It is, however, possible to continuouslychange the pulse intensities and the pulse widths correspondingly to thechange in the linear recording velocity.

[0075] On the other hand, in the case where data are to be recorded inthe CLV format, since the linear recording velocity is usually changedto be an integer multiple of the original linear velocity such as 2×velocity, a 4× velocity, a 6× velocity, an 8× velocity or the like andV_(H)/V_(L) is relatively large, it is preferable to change the pulseintensities and the pulse widths for every linear recording velocity.

[0076] The linear recording velocity V_(H) is selected so as to satisfypreferably 1.1≦V_(H)/V_(L) and more preferably 1.2≦V_(H)/V_(L). IfV_(H)/V_(L) is small, it is unnecessary for the pulse intensities andthe pulse widths to be set different between the linear recordingvelocities V_(L) and V_(H). On the other hand, if V_(H)/V_(L) is toolarge, since the advantage of the present invention is slight, thelinear recording velocities V_(L) and V_(H) are determined so as tosatisfy preferably V_(H)/V_(L)≦8 and more preferably V_(H)/V_(L)<4.

[0077] Next, the write strategies applicable to the present inventionwill be described in detail below with reference to the accompanyingdrawings.

[0078]FIG. 4 is a drawing showing the write strategy when data are to berecorded in an optical recording medium using the (1, 7) RLL modulationcode, wherein FIG. 4(a) is a drawing showing the write strategy forforming a 3T signal, FIG. 4(b) is a drawing showing the write strategyfor forming a 4T signal, FIG. 4(c) is a drawing showing the writestrategy for forming a 5T signal and FIG. 4(d) is a drawing showing thewrite strategy for forming a 5T signal to a 8T signal.

[0079] As shown in FIGS. 4(a) to 4(d), in this embodiment, when data areto be recorded in an optical recording medium, the power of a recordingbeam is modulated among three intensities (three values): the recordingpower Pw, the bias power Pbi and the bottom power Pbo. The intensity ofthe recording power Pw is set to be a level at which a phase changematerial contained in the recording layer can be melted by theirradiation with the recording beam so that the intensity of therecording power Pw is set to be PwH when data are to be recorded at thelinear recording velocity V_(H) and that it is set to be PwL when dataare to be recorded at the V_(L). The intensity of the bias power Pbi isset to be a level at which the phase change material contained in therecording layer can be heated to a temperature equal to or higher thanthe crystallization temperature thereof by the irradiation with therecording beam so that the intensity of the bias power Pbi is set to bePbiH when data are to be recorded at the linear recording velocity V_(H)and that it is set to be PbiL when data are to be recorded at the V_(L).The intensity of the bottom power Pbo is set to be a level at which themelted phase change material can be cooled even if it is irradiated withthe recording beam so that the intensity of the bottom power Pbo is setto be PboH when data are to be recorded at the linear recording velocityV_(H) and that it is set to be PboL when data are to be recorded at thelinear recording velocity V_(L).

[0080] As described above, the values of the recording power PwH and PwLand the bias power PbiH and PbiL are set so as to satisfy PbiH/PbiL<1and (PbiH/PwH)/(PbiL/PwL)<1.

[0081] In the description regarding FIG. 4, when data are to be recordedat the linear recording velocity V_(H), the recording power PwH, thebias power PbiH and the bottom power PboH will be merely referred to asthe recording power Pw, the bias power Pbi and the bottom power Pbo,respectively, and when data are to be recorded at the linear recordingvelocity V_(L), the recording power PwL, the bias power PbiL and thebottom power PboL will be merely referred to as the recording power Pw,the bias power Pbi and the bottom power Pbo, respectively.

[0082] Further, in the description regarding FIG. 4, when data are to berecorded at the linear recording velocity V_(H), TtopH, TmpH, TlpH andTclH will be merely referred to as Ttop, Tmp, Tlp and Tcl, respectively,and when data are to be recorded at the linear recording velocity V_(L),TtopL, TmpL, TlpL and TclL will be merely referred to as Ttop, Tmp, Tlpand Tcl, respectively.

[0083] As shown in FIG. 4(a), when a 2T signal is to be formed in anoptical recording medium, the number of upward pulses is set to be “1”and a cooling pulse is added after the upward pulse. The number ofupward pulses is defined as the number of times the intensity of therecording beam is raised to the recording power Pw. In thisspecification, among upward pulses of the recording beam, the firstpulse is called a top pulse, the last pulse is called a last pulse andpulses between the top pulse and the last pulse are called multi-pulses.In the case where the number of upward pulses is “1”, the top pulsecorresponds to a multi-pulse.

[0084] Therefore, when a 2T signal is to be formed, the intensity of therecording beam is set to be the bias power Pbi before time t11, therecording power Pw during a period (Ttop) from the time t11 to the timet12, the bottom power Pbo during a period (Tcl) from the time t12 to thetime t13, and the bias power Pbi after the time t13.

[0085] Further, as shown in FIG. 4(b), when a 3T signal is to be formedin an optical recording medium, the number of upward pulses is set to be“2” and a cooling pulse is added after the upward pulses. As shown inFIG. 4(b), in the case where the number of upward pulses is “2”, theupward pulses are constituted as the top pulse and the last pulse.

[0086] Therefore, when a 3T signal is to be formed, the intensity of therecording beam is set to be the bias power Pbi before the time t21, therecording power Pw during a period (Ttop) from the time t21 to the timet22 and a period (Tlp) from the time t23 to the time t24, the bottompower Pbo during a period (Toff) from the time t22 to the time t23 and aperiod (Tcl) from the time t24 to the time t25, and the bias power Pbiafter the time t25.

[0087] Furthermore, as shown in FIG. 4(c), when a 4T signal is to beformed in an optical recording medium, the number of upward pulses isset to be “3” and a cooling pulse is added after the upward pulses.Therefore, when a 4T signal is to be formed, the intensity of therecording beam is set to be the bias power Pbi before the time t31, therecording power Pw during a period (Ttop) from the time t31 to the timet32, a period (Tmp) from the time t33 to the time t34 and a period (Tlp)from the time t35 to the time t36, the bottom power Pbo during a period(Toff) from the time t32 to the time t33, a period (Toff) from the timet34 to the time t35 and a period (Tcl) from the time t36 to the timet37, and the bias power Pbi after the time t37.

[0088] Moreover, when a 5T signal to a 8T signal are to be formed in anoptical recording medium, the number of upward pulses is set to be “3”and a cooling pulse is added after the upward pulses. Therefore, when a5T signal to a 8T signal are to be formed in an optical recordingmedium, the number of multi-pulses is set to be “5” to “8”,respectively. In this case, the intensity of the recording beam is setto be the recording power Pw during a period (Ttop) from the time t41 tothe time t42, periods (Tmp) from the time t43 to the time t44, from thetime t45 to the time t46 and the like, and a period (Tlp) from the timet47to the time t48, the bottom power Pbo during periods (Toff) from thetime t42 to the time t43, from the time t46 to the time t47 and thelike, a period (Toff) from the time t46 to the time t47 and a period(Tcl) from the time t48 to the time t49, and the bias power Pbi duringother periods.

[0089] Thus, at a region where a recording signal, namely, a 2T signalto a 8T signal, is to be formed, a phase change material is melted bythe irradiation with the recording beam having the recording power Pwand quickly cooled by the cooling pulse, thereby becoming an amorphousphase. On the other hand, at other regions, the phase change material isheated to a temperature equal to or higher than the crystallizationtemperature thereof by the radiation with the recording beam having thebias power Pbi and gradually cooled by moving the recording beam away,thereby being crystallized.

[0090] In the present invention, in the case of V_(H)>V_(L), preferably,1.1≦V_(H)/V_(L), jitter of reproduced signal from data recorded at awide range of linear recording velocities can be reduced by setting thepulse intensities (power levels) in the above write strategy so as tosatisfy PbiH/PbiL<1 and (PbiH/PwH)/(PbiL/PwL)<1 and set the pulse widthsso as to satisfy TclH/TclL<1, TmpH/TmpL≦1, TtopH/TtopL≦1 and1≦TlpH/TlpL.

[0091] The present invention can be applied to a recording method inwhich the pulse intensities and the pulse widths used for actualrecording are determined by performing test recording at a particularlinear recording velocity prior to recording data at the linearrecording velocity in the CLV format. Further, the present invention canbe applied to a recording method in which the pulse intensities and thepulse widths used for actual recording are determined by performing testrecording using at least one linear recording velocity prior torecording data in the CAV format.

[0092] When test recording is to be performed, at least one parameter isselected from among parameters regarding pulse intensity and parameterregarding pulse width and test recording is performed on an opticalrecording medium by changing the value thereof. Then, a signal recordedby test recording is reproduced and error and jitter are measured,thereby judging the quality of the reproduced signal. When the qualityof the reproduced signal is low, the parameter is changed and/or anotherparameter is changed and test recording is again performed. Optimumrecording conditions used for actual recording are obtained by repeatingthese procedures. Since data are usually recorded in a disk-like opticalrecording medium from the inner circumferential portion, test recordingis preferably performed at the inner circumferential portion and, morepreferably performed at both the inner circumferential portion and theouter circumferential portion. In particular, in the CAV format, since alinear velocity at the inner circumferential portion is greatlydifferent from that at the outer circumferential portion, it ispreferable to perform test recording at both the inner circumferentialportion and the outer circumferential portion. Test recording is usuallyperformed in a test recording region provided separately from datarecording regions.

[0093] Hereinafter, explanation will be made as to a case where thepresent invention is applied to a recording method constituted so as todetermine optimum recording conditions by test recording.

[0094] In a first method using test recording, a plurality of pulseintensities and pulse widths are given for each of linear recordingvelocities V_(L) and V_(H). When data are to be recorded at a particularlinear recording velocity, test recording is utilized for selecting thepulse intensity and the pulse width used for actual recording from amongthe plurality of pulse intensities and pulse widths assigned to thelinear recording velocity. Further, in the first method, the pulseintensity and the pulse width used for actual recording at each linearrecording velocity may be defined as a function of the linear recordingvelocity so that a plurality of the functions are provided for eachlinear recording velocity. In this case, the functions actually used ateach linear recording velocity are determined by test recording. Theplurality of combinations of the pulse intensity and the pulse width orthe functions provided for each linear recording velocity may be storedin an optical recording apparatus or recorded in an optical recordingmedium. In this specification, the thus provided plurality ofcombinations of the pulse intensity and the pulse width or the functionsare sometimes called “information for setting recording conditions”.

[0095] Next, a second method using test recording will be explained. Inthe second method, a reference linear recording velocity has to be givenand recommended values of pulse intensity and pulse width at the linearrecording velocity have to be given. It is assumed that the referencelinear recording velocity is V_(L) and a linear recording velocity usedfor test recording is V_(H). The linear recording velocity V_(H) is alinear recording velocity used for actual recording in the CLV format.On the other hand, in the CAV format, as described above, the triallinear recording velocity V_(H) is determined by dividing the linearrecording velocity between the lowest linear recording velocity and thehighest linear recording velocity into a plurality of linear recordingvelocity regions and selecting a linear recording velocity in thevicinity of the center of each linear recording velocity region.Similarly to the relationship between V_(L) and V_(H), the trial linearrecording velocity V_(H) satisfies V_(H)>V_(L), preferably,1.1≦V_(H)/V_(L). It is possible to obtain optimum recording conditionsat the recording velocity V_(H) higher than the reference linearrecording velocity V_(L) and that close to the recording velocity V_(H)with a few procedures by setting PwH and PbiH so as to satisfyPbiH/PbiL<1 and (PbiH/PwH)/(PbiL/PwL)<1 where PwL and PbiL arerecommended values of Pw and Pbi at the linear recording velocity V_(L)and PwH and PbiH are Pw and Pbi when the test recording is performed atthe linear recording velocity V_(H) and performing the test recording.

[0096] The optimum value of each of Tcl, Tmp, Ttop and Tlp can beobtained in a similar manner. Specifically, when TclL is given as therecommended value of Tcl at the reference linear recording velocityV_(L), if the test recording is performed by setting TclH so as tosatisfy TclH/TclL<1 where TclH is Tcl when the test recording isperformed at the linear recording velocity V_(H), it is possible toobtain the optimum value of Tcl at the recording velocity V_(H) and thatclose to the recording velocity V_(H) with a few procedures.

[0097] Further, when TmpL is given as the recommended value of Tmp atthe reference linear recording velocity V_(L), if the test recording isperformed by setting TmpH so as to satisfy TmpH/TmpL≦1 where TmpH is Tmpwhen the test recording is performed at the linear recording velocityV_(H), it is possible to obtain the optimum value of Tmp at therecording velocity V_(H) and that close to the recording velocity V_(H)with a few procedures.

[0098] Furthermore, when TtopL is given as the recommended value of Ttopat the reference linear recording velocity V_(L), if the test recordingis performed by setting TtopH so as to satisfy TtopH/TtopL≦1 where TtopHis Ttop when the test recording is performed at the linear recordingvelocity V_(H), it is possible to obtain the optimum value of Ttop atthe recording velocity V_(H) and that close to the recording velocityV_(H) with a few procedures.

[0099] Moreover, when TlpL is given as the recommended value of Tlp atthe reference linear recording velocity V_(L), if the test recording isperformed by setting TlpH so as to satisfy TlpH/TlpL≦1 where TlpH is Tlpwhen the test recording is performed at the linear recording velocityV_(H), it is possible to obtain the optimum value of Tlp at therecording velocity V_(H) and that close to the recording velocity V_(H)with a few procedures.

[0100] The present invention can be also applied to the test recordingwhen data are to be recorded at a linear recording velocity lower thanthe reference linear recording velocity. In this case, a referencelinear recording velocity V_(H) and a linear recording velocity V_(L)used for the test recording are first set so as to satisfy1.1≦V_(H)/V_(L). Further, PwL and PbiL are set so as to satisfyPbiH/PbiL<1 and (PbiH/PwH)/(PbiL/PwL)<1 where the symbols PwH and PbiHare recommended values of Pw and Pbi at the linear recording velocityV_(H) and the symbols PwL and PbiL are Pw and Pbi when the testrecording is to be performed at the linear recording velocity V_(L), andthe test recording is performed. As a result, it is possible to obtainoptimum recording conditions at the recording velocity V_(L) lower thanthe reference linear recording velocity V_(H) and that close to therecording velocity V_(L) with a few procedures. Each of the optimumvalues of Tcl, Tmp, Ttop and Tlp can be obtained in a similar manner.

[0101] It is sufficient for the optical recording apparatus to read thereference linear recording velocity and the recommended values of thepulse intensity and the pulse width when test recording is to beperformed, and both may be stored in the optical recording apparatus orrecorded in the optical recording medium. In this specification, therecommended values of the pulse intensity and the pulse width meanvalues recommended by an optical recording medium manufacturer, oroptimum values or recommended values prescribed in the standard of therecording system. In this specification, these recommended values aresometimes called “information for setting recording conditions”.

[0102] The reference linear recording velocity used in the abovedescribed method is not necessarily equal to the original linearrecording velocity in a recording system to which the present inventionis applied and may assume an arbitrary value. For example, in the casewhere the original linear recording velocity is 3.5 m/s, the referencelinear recording velocity may be 2× velocity, namely, 7.0 m/s. Further,in the case where this recording method is applied, it is not necessaryto record data at a plurality of linear recording velocities, and datamay be recorded only at, for example, four times the velocity of thereference linear recording velocity.

[0103] The second method utilizing test recording is as described in theforegoing.

[0104] The present invention is most effective at a linear recordingvelocity range where V_(H)/V_(L) is within the above range and theminimum value of the plurality of linear recording velocities or thechanging linear recording velocity is preferably equal to or larger than2 m/s, more preferably equal to or larger than 2.5 m/s, most preferablyequal to or larger than 3 m/s.

[0105] When V_(H)/V_(L) is within the above range, it is preferable that0.2≦PbiH/PbiL<1, 0.5≦(PbiH/PwH)/(PbiL/PwL)<1, 0≦TclH/TclL<1,0.2≦TmpH/TmpL≦1, 0.2≦TtopH/TtopL≦1 and 1≦TlpH/TlpL≦3 are satisfied andit is more preferable that 0.3≦PbiH/PbiL<0.99,0.5≦(PbiH/PwH)/(PbiL/PwL)<0.99, 0.05≦TclH/TclL<0.99, 0.3≦TmpH/TmpL≦0.99,0.3≦TtopH/TtopL≦0.99 and 1.01≦TlpH/TlpL≦3 are satisfied. If the ratio ofpulse intensities or a ratio of pulse width is outside of the aboverange, it is difficult to reduce jitter when data are recorded at alinear recording velocity within a range where V_(H)/V_(L) is within theabove range. For example, when PbiH and PbiL are set so as to satisfyPbiH/PbiL<0.2, the efficiency of erasing data at the linear recordingvelocity V_(H) is lowered and direct overwriting of data cannot beeffected.

[0106] In the present invention, it is preferable in the recordingwaveform shown in FIGS. 2 and 4(b) and having two upward pulses in therecording pulse section and in the recording waveform shown in FIGS. 3and 4(a) and having only one upward pulse in the recording pulse sectionthat PbiH/PbiL, (PbiH/PwH)/(PbiL/PwL), Tcl and TtopH/TtopL lie withinthe above stated ranges and it is preferable in the recording waveformshown in FIGS. 2 and 4(b) that TlpH/TlpL also lies within the abovestated range.

[0107] Since the first upward pulse is raised from the bias power Pbi,if the width Ttop of the first upward pulse is smaller that the widthTmp of the other pulse, the temperature of the recording layer is notsufficiently increased and it is sometimes difficult to form a recordmark having a predetermined length. Therefore, it is preferable to setthe width Ttop of the first upward pulse to smaller that the width Tmpof the other pulse so as to satisfy 1≦Ttop/Tmp. However, if Ttop/Tmp istoo large, since the advantage of the multi-pulse recording is lowered,it is preferable to set the width Ttop of the first upward pulse tosmaller that the width Tmp of the other pulse so as to satisfyTtop/Tmp≦3.

[0108] Further, the length of a record mark can be adjusted bycontrolling the width Tlp of the last upward pulse. However, since theadvantage of the multi-pulse recording is lowered if Tlp/Tmp is toosmall or too large, it is usually preferable to set Tlp so as to satisfy0.5≦Tlp/Tmp ≦2.

[0109] In the present invention, it is preferable to record data bysetting the intensity Pbo of a downward pulse following the upward pulsein the recording pulse section so as to satisfy Pbo≦Pbi. This is becausethe advantage of proving the downward pulse is prevented from beinglowered. However, the power level of the downward pulse has to be largerthan 0 in order to enable the tracking servo operation. If Pbo is set tobe equal to Pbi, the burden on the control means of the opticalrecording apparatus can be reduced. When the level Pbo of all downwardpulses is the same and Pbo is equal to Pbi, the cooling pulse does notexist. However, the cooling pulse may be controlled separately fromother downward pulses. In the present invention, it is preferable toprovide a cooling pulse, since jitter can be reduced by controlling thecooling pulse in accordance with the linear recording velocity.

[0110] The intensity of the first upward pulse and that of the lastupward pulse may be different from the intensity Pw of an upwardpulse(s) therebetween. In the case of expressing the intensity of thefirst upward pulse as Ptop and the intensity of the last upward pulse asPlp, Ptop may be set to be higher than Plp instead of setting Ttop to behigher than Tmp, and Plp may be set to be higher or lower than Pwinstead of setting Tlp to be higher or lower than Tmp. Further, Ttop andPtop may be controlled together and Tlp and Plp may be controlledtogether. However, it is preferable to set Ptop equal to PW and Plpequal to Pw in order to reduce the burden on the control means of theoptical recording apparatus.

[0111] The present invention is applied to a data rewritable typesystem. Therefore, since Pbi functions as an erasing power, the lowerlimit of Pbi can be determined based on the composition of the recordinglayer so as to crystallize a record mark, and the overwriting linearvelocity and the like and the upper limit of Pbi can be determined so asto prevent the recording layer from changing to an amorphous state andprevent the recording layer from being damaged by repeating irradiationwith a recording beam.

[0112] In the present invention, it is not absolutely necessary toalways set Ttop to be equal to Tlp for forming record marks having thesame signal length. For example, Ttop may be properly controlled forforming each record mark in accordance with the length of the recordmark formed immediately before and Tlp may be properly controlled forforming each record mark in accordance with the length of the recordmark to be formed immediately after.

[0113] The above mentioned Japanese Patent Application Laid Open No.10-106008, Japanese Patent Application Laid Open No. 11-232652 andJapanese Patent Application Laid Open No. 2000-155945 disclose that thepulse width and the pulse height are controlled in accordance with thelinear recording velocity in the multi-pulse recording. However,Japanese Patent Application Laid Open No. 10-106008 and Japanese PatentApplication Laid Open No. 11-232652 do not disclose that Pbi and theratio between Pbi and Pw are controlled in accordance with the linearrecording velocity. Further, unlike the present invention, JapanesePatent Application Laid Open No. 2000-155945 specifies PbiL/PwL<PbiH/PwH.

[0114] Japanese Patent Application Laid Open No. 2000-155945 is directedto a CD-RW whose recording track pitch is wider than a DVD andexperiments conducted regarding the CD-RW are described therein. To thecontrary, as described later, the present invention is directed to anoptical recording medium in which data can be recorded at higher densitythan that in the CD-RW. Further, the present invention is directed to anoptical recording medium whose recording track pitch is equal to ornarrower than that of the DVD-RW, namely, 0.74 μm. As a result, it canbe considered that the relationship between PbiL/PwL and PbiH/PwH isreverse to that described in Japanese Patent Application Laid Open No.2000-155945. Moreover, it is effective to apply the present invention toan optical recording medium whose recording track pitch is equal to ornarrower than 0.8 μm. However, since the present invention is not soadvantageous when applied to an optical recording medium whose recordingtrack pitch is too narrow, it is preferable to apply the presentinvention to an optical recording medium whose recording track pitch isequal to or wider than 0.1 μm.

[0115] The present invention is particularly advantageous when data arerecorded so as to satisfy n·Tw≦20 ns, particularly, n·Tw≦18 ns at thehighest linear recording velocity where Tw is the width of a detectionwindow and n·Tw is the signal length corresponding to the shortestrecord mark. In other words, the present invention is particularlyadvantageous when the signal length n·Tw corresponding to the shortestrecord mark is equal to or longer than a certain value.

[0116] The shortest signal length n·Tw affects the data transfer rate,and as n·Tw is shorter, the data transfer rate becomes higher. In orderto shorten the shortest signal length n·Tw, it is necessary to recorddata at high density by decreasing the spot diameter of the laser beamused for recording and reproducing data or increase the linear recordingvelocity. In the case where the laser output is kept constant, theamount of heat that accumulates in the recording layer becomes smalleras the linear recording velocity is higher. On the other hand, a laserbeam having a shorter wavelength is employed or an objective lens havinga larger numerical aperture is employed in a laser beam projectingoptical system in order to decrease the spot diameter of a laser beambut in such a case, since energy per unit area of the laser beam spotbecomes high, heat tends to accumulate in the recording layer when dataare recorded. Therefore, the amount of heat accumulated in the recordinglayer depends upon the spot diameter of the laser beam and the linearrecording velocity. If heat tends to accumulate in the recording layer,the accumulated heat is conducted in the planar direction of therecording layer during recording and a portion of the record marks tendsto be re-crystallized, in other words, self-erasing tends to occur. Ifself-erasing occurs, jitter of the reproduced signal increases. Inexperiments conducted by the inventors of the present invention, it wasfound that in the case where n·Tw exceeds 20 ns, the effect of thelinear recording velocity becomes relatively great to make self-erasingunlikely to occur and that in the case where n·Tw is equal to or shorterthan 20 ns, the effect of reducing the spot diameter of the laser beambecomes relatively great to make self-erasing likely to occur.Therefore, in the case where n·Tw is equal to or shorter than 20 ns, thepresent invention enables jitter due to self-erasing to be markedlyprevented by setting PbiH and PbiL so as to satisfy PbiH/PbiL<1, namely,setting Pbi to be lower as the linear recording velocity increases.

[0117] In a phase change type optical recording medium, in order toenable data to be rewritten, the composition of the recording layer andthe linear recording velocity of the medium are determined so that arecording mark can be erased (crystallized) by heating. As a result, indata rewritable phase change type optical recording medium, self erasingtends to occur due to heat accumulated in the recording layer.Therefore, the present invention is particularly useful in the casewhere a phase change type optical recording medium is used as a datarewritable optical recording medium.

[0118] The reason why it is preferable in the present invention to setTcl to be larger as the linear recording velocity is lower is to preventself erasing. Further, the reason why it is preferable in the presentinvention to set Tmp and Ttop to be smaller as the linear recordingvelocity is higher is to prevent self erasing due to heat held in therecording layer.

[0119] Since a laser diode has limited responsivity, the laser diodecannot properly be activated when the shortest record mark is to beformed if n·Tw is too short. Therefore, n·Tw is preferably set tosatisfy 2 ns≦n·Tw, more preferably to satisfy 4 ns≦n·Tw.

[0120] The shortest signal length corresponds to a 2T signal in the 1-7Modulation Code and in such a case, n is equal to 2. The shortest signallength corresponds to a 3T signal in the 8-16 Modulation Code and insuch a case, n is equal to 3.

[0121] The so-called data transfer rate interrelates with not only n·Twbut also formatting efficiency, and even if n·Tw is the same, the datatransfer rate becomes lower as the format efficiency is lower.Therefore, a recording velocity can be more directly expressed by n·Tw.Among conventional optical recording disks, in a DVD-RAM4.7 having acapacity of 4.7 GB/surface, the linear recording velocity is 8.2 m/s,the data transfer rate is 22 Mbps and n·Tw is 51.41 ns. In a DVD-RWhaving a capacity of 4.7 GB/surface, the linear recording velocity is3.5 m/s, the data transfer rate is 11 Mbps and n·Tw is 78.48 ns. Since,as mentioned above, n·Tw≦20 ns is satisfied in the present invention,n·Tw of the present invention is very short in comparison with those inthe conventional optical recording disks.

[0122] In the present invention, the wavelength λ of the laser beam usedfor recording data and the numerical aperture NA of the objective lensof the laser beam projecting optical system are set so as to satisfyλ/NA≦680 nm, preferably λ/NA≦630 nm. If λ/NA is too large, it isdifficult to record data at high density because the pitch of therecording track has to be increased. Further, if λ/NA is too large, theadvantages obtained by applying the present invention are slight becauseit is difficult to considerably increase the energy density of the beamspot of the laser beam and heat does not easily accumulate in therecording layer. However, since available laser beam wavelengths andavailable objective lens numerical are limited and it is difficult toemploy a laser beam having an extremely short wavelength and anobjective lens having an extremely large numerical aperture, it isusually preferable to set λ and NA so as to satisfy 350 nm≦λ/NA.

[0123] In the recording waveform, the ratio of the width of an upwardpulse to the width of the set consisting of the upward pulse and thefollowing downward pulse, namely, the duty ratio, is preferably 0.3 to0.9. If the duty ratio is too small, it is undesirably necessary to usea laser beam having a high power. On the other hand, if the duty ratiois too large, the width, length and shape of the record marks tend tobecome irregular and, as a result, jitter of the reproduced signal tendsto increase.

[0124] As described in the above mentioned Japanese Patent ApplicationLaid Open No. 2000-155945, a downward pulse whose power level is lowerthan the erasing power may be inserted immediately before the firstupward pulse and an upward pulse whose intensity is lower than the firstupward pulse may be inserted immediately before the first upward pulse,thereby assisting increase in the temperature of the recording layer.

[0125] In the present invention, it is unnecessary for the recordingpulse section for forming a record mark having a signal length kT(wherek is an integer equal to or larger than 1 and T is a reference clockwidth) to have a width of kT. If the laser projecting time period is setto be kT, the width of the recording pulse section is usually set to beshorter than the signal length to be recorded because the length of arecord mark sometimes becomes longer owing to heat transfer in thelongitudinal direction of the recording track. Although the number ofupward pulses in the recording pulse section for recording a kT signalis set to be (k−2) in FIGS. 1 to 3, the number of upward pulses is notlimited to (k−2) and the number thereof may be (k−1) as shown in FIG. 4.Further, in the present invention, the modulation code is notparticularly limited.

[0126] The present invention is particularly advantageous when it isapplied to the mark edge recording method.

[0127] In a drive apparatus for an optical recording medium, it isordinary to superpose a high frequency signal whose frequency is anorder or more of magnitude higher than the recording frequency, forexample, a high frequency signal having a frequency of several hundredsmegahertz, on the drive signal for modulating the intensity of the laserbeam for recording, reproducing and erasing data. A direct current laserbeam as termed in this specification includes a laser beam modulated bya direct current on which such a high frequency signal is superposed.

[0128] Explanation will next be made regarding an example of theconfiguration of an optical recording medium to which the presentinvention is applied.

[0129] The Structure Shown in FIG. 5

[0130] One configuration of an optical recording medium according to thepresent invention is shown in FIG. 5. The optical recording mediumincludes a first dielectric layer 31, a recording layer 4, a seconddielectric layer 32, a reflective layer 5 and a protective layer 6 on alight transmittable substrate 2 in this order and a laser beam forrecording and reproducing data is impinged onto the light transmittablesubstrate 2.

[0131] The Light Transmittable Substrate 2

[0132] The light transmittable substrate 2 has a property oftransmitting a laser beam for recording or reproducing data. The lighttransmittable substrate 2 usually has a thickness of 0.2 to 1.2 mm andpreferably has a thickness of 0.4 to 1.2 mm. The light transmittablesubstrate 2 can be formed of resin but may instead be formed of glass.Grooves (guide grooves) 2G usually formed in an optical recording mediumare present on the laser beam incident side and convex portions presentbetween neighboring grooves 2G are lands 2L.

[0133] In the present invention, the lands and/or the grooves can beutilized as a recording track.

[0134] The First Dielectric Layer 31 and the Second Dielectric Layer 32

[0135] These dielectric layers serve to prevent oxidization anddegradation of the recording layer and block heat transferred from therecording layer when data are recorded or discharge it in a planardirection, thereby protecting the light transmittable substrate 2.Further, the degree of modulation can be improved by providing thesedielectric layers. Each of the dielectric layers may be formed bysuperposing two or more dielectric layers having different compositions.

[0136] It is preferable to employ compounds containing at least onemetal element selected from among Si, Ge, Zn, Al, rare earth elementsand the like as the dielectric material used for forming thesedielectric layers. Oxide, nitride or sulfide is preferably used as thecompound for forming these dielectric layers and a mixture containingtwo or more these compounds may be used for forming these dielectriclayers.

[0137] In the case where it is required for an optical recording mediumto have a quick cooling structure, it is preferable to form thedielectric layers, particularly the second dielectric layer, of adielectric material having high thermal conductivity. As a dielectricmaterial having high thermal conductivity, a mixture of zinc sulfide andsilicon oxide (ZnS—SiO₂), aluminum nitride, aluminum oxide, siliconnitride, tantalum oxide and the like are preferable and oxide and/ornitride of aluminum and oxide and/or nitride of silicon are particularlypreferable. In the case of using ZnS—SiO₂ as a dielectric material, itis preferable to employ ZnS—SiO₂ containing 30 to 60 mol % of SiO₂. Ifthe content of SiO₂ is too small, the thermal conductivity of themixture becomes too low. On the other hand, if the content SiO₂ is toolarge, the dielectric layer is apt to peel off from the other layersduring long storage because the adhesion between the dielectric layerand other layers is insufficient.

[0138] In the optical recording medium having a quick cooling structure,the thermal conductivity of the second dielectric layer is preferablyequal to or higher than 1 W/mK and more preferably equal to or higherthan 1.5 W/mK. There is no particular upper limit on the thermalconductivity of the second dielectric layer but the thermal conductivityof the material usable for forming the dielectric layer is usually equalto or lower than about 20 W/mK. In this specification, the thermalconductivity of the second dielectric layer is not a value measured froma thin film-like dielectric layer but a value measured from a bulk-likedielectric material.

[0139] The thickness of each of the first dielectric layer and thesecond dielectric layer can be properly determined so as to sufficientlyserve as a protection layer and sufficiently improve the degree ofmodulation. Usually, the thickness of the first dielectric layer 31 ispreferably 30 to 300 nm and more preferably 50 to 250 nm and thethickness of the second dielectric layer 32 is preferably 10 to 50 nm.It is preferable for a write-once type optical recording medium to havea quick cooling structure so that an amorphous record mark does notreadily crystallize, and for this purpose, the thickness of the seconddielectric layer 32 is preferably equal to or thinner than 30 nm andmore preferably equal to or thinner than 25 nm.

[0140] It is preferable to form each of the dielectric layers using thesputtering process.

[0141] The Recording Layer 4

[0142] The composition of the recording layer is not particularlylimited and the material for forming the recording layer can be properlyselected from among various phase change materials but it is preferableto select a material containing at least Sb and Te. Since thecrystallization temperature of the recording layer consisting of Sb andTe only is a low 130° C. and the storage reliability of the recordinglayer is not sufficiently high, it is preferable to add other elementsto the recording layer for increasing the crystallization temperature ofthe recording layer. In this case, it is preferable to add at least oneelement selected from among In, Ag, Au, Bi, Se, Al, P, Ge, H, Si, C, V,W, Ta, Zn, Ti, Sn, Pb, Pd and rare earth elements (Sc, Y andlanthanide). Among these, it is preferable to add at least one elementselected from among rare earth elements, Ag, In and Ge, since they canparticularly improve the storage reliability.

[0143] The material containing Sb and Te preferably has the followingcomposition.

(Sb_(x)Te_(1−x))_(1−y)M_(y)  Formula I

[0144] where M is an element other than Sb and Te. It is preferable thatx is equal to or larger than 0.2 and equal to or smaller than 0.8 and yis equal to or larger than 0 and equal to or smaller than 0.4 and it ismore preferable that x is equal to or larger than 0.5 and equal to orsmaller than 0.85 and y is equal to or larger than 0.01 and equal to orsmaller than 0.2. Concretely, x may be properly determined in accordancewith the linear recording velocity and heat design of the opticalrecording medium.

[0145] If x representing the amount of Sb is too small, thecrystallizing rate becomes low to make it difficult to erase a recordmark at a relatively high linear velocity. Further, since the reflectioncoefficient of a crystalline region of the recording layer becomes low,the power of the reproduced signal becomes low. If x is extremely low,it is difficult to record data in the recording layer.

[0146] To the contrary, if x is too large, the power of the reproducedsignal becomes low because the difference in the reflection coefficientsbetween a crystalline region and an amorphous region of the recordinglayer becomes low.

[0147] The element M is not particularly limited but it is preferable toselect at least one element from the above mentioned elements capable ofimproving the storage reliability. If y representing the amount of theelement M is too large, the crystallizing rate becomes too high and thepower of the reproduced signal becomes low.

[0148] The thickness of the recording layer is preferably greater than 4nm and equal to or thinner than 50 nm and more preferably 5 to 30 nm. Ifthe recording layer is too thin, a crystalline phase is hard to grow andit is difficult to crystallize the recording layer. On the other hand,if the recording layer is too thick, the heat capacity of the recordinglayer becomes large, which makes it difficult to record data and lowersthe power of the reproduced signal.

[0149] It is preferable to form the recording layer using the sputteringprocess.

[0150] In the present invention, the structure of the recording layer isnot particularly limited and the present invention can be applied to anoptical recording medium having a multi-layered recording layer asdescribed in, for example, Japanese Patent Application Laid Open No.8-221814 or Japanese Patent Application Laid Open No. 10-226173.

[0151] The Reflective Layer 5

[0152] The material for forming the reflective layer is not particularlylimited and the reflective layer may be formed of a metal or semi-metalsuch as Al, Au, Ag, Pt, Cu, Ni, Cr, Ti, Si or the like or an alloycontaining one or more kinds of these elements.

[0153] In the case where it is required for the optical recording mediumto have a quick cooling structure, it is preferable to form thereflective layer of a material having high thermal conductivity. Ag orAl is preferably employed as the material having high thermalconductivity. However, since a reflective layer made of Ag or Al alonedoes not have sufficient corrosion resistance, it is preferable to addan element to the reflective layer that improves the corrosionresistance thereof.

[0154] However, since addition of an element other than Ag or Al to thereflective layer lowers the thermal conductivity of the reflectivelayer, it is preferable to employ Ag, which has higher thermalconductivity, as a main component. Illustrative examples ofsub-ingredients to be added together with Ag include Mg, Pd, Ce, Cu, Ge,La, S, Sb, Si, Te and Zr. It is preferable to use at least one of thesesub-ingredients and more preferably two or more thereof. The amount ofeach of the sub-ingredients to be added to the reflective layer is 0.05to 2.0 atomic % and preferably 0.2 to 1.0 atomic % and the total amountof the sub-ingredients to be added to the reflective layer is 0.2 to 5.0atomic % and preferably 0.5 to 3.0 atomic %. If the amount of thesub-ingredients added to the reflective layer is too small, corrosionresistance cannot be sufficiently improved. On the other hand, if theamount of the sub-ingredients added to the reflective layer is toolarge, the thermal conductivity of the reflective layer is low.

[0155] In the case where it is required for the optical recording mediumto have a quick cooling structure, the thermal conductivity of thereflective layer is preferably equal to or higher than 100 W/mK and morepreferably equal to or higher than 150 W/mK. The thermal conductivity ofthe reflective layer can be calculated using the Wiedemann-Franz lawbased on the electrical conductivity of the reflective layer measured bythe four-probe method, for example. There is no particular upper limiton the thermal conductivity of the reflective layer. In other words, itis possible to employ pure silver having a thermal conductivity of 250W/mK, which is the highest among those of materials usable forreflective layer.

[0156] Usually, the thickness of the reflective layer is preferably 10to 300 nm. If the thickness of the reflective layer is thinner than 10nm, a reflective layer having a sufficiently high reflective coefficientcannot be obtained. On the other hand, increasing the thickness of thereflective layer beyond 300 nm produces only a small improvement in thereflective coefficient of the reflective layer that is disproportionateto the increase in cost. It is preferable to form the reflective layerusing a gas phase growth process such as a sputtering process, a vapordeposition process or the like.

[0157] The Protective Layer 6

[0158] The protective layer 6 is provided in order to improve theabrasion resistance and corrosion resistance of the optical recordingmedium. The protective layer can be preferably formed of any of variousorganic materials and can be particularly preferably formed byirradiating a radiation curable type compound or the components thereofwith an electron beam, an ultraviolet ray or the like, thereby curingit. The thickness of the protective layer is usually about 0.1 to 100 μmand the protective layer is usually formed using a spin coating process,a gravure coating process, a spray coating process, a dip coatingprocess or the like.

[0159] The Structure Shown in FIG. 6

[0160] Another configuration of an optical recording medium according tothe present invention is shown in FIG. 6. This optical recording mediumincludes a reflective layer 5 made of a metal or semi-metal, a seconddielectric layer 32, a recording layer 4, a first dielectric layer 31and a light transmittable substrate 2 on a support substrate 20 in thisorder. A laser beam for recording and reproducing data is impinged ontothe light transmittable substrate 2. An intermediate layer such as adielectric layer may be formed between the support substrate 20 and thereflective layer 5.

[0161] As the light transmittable substrate 2 of this optical recordingmedium, a resin plate or a glass plate having substantially the samethickness of that of the light transmittable substrate 2 shown in FIG. 5may be employed. However, it is preferable to make the lighttransmittable substrate 2 thinner in order to make the numericalaperture of the recording and reproducing optical system larger andrecord data at high density. In such a case, a light transmittablesupport 2 having a thickness of 20 to 300 μm is preferably selected. Ifthe light transmittable support 2 is too thin, the optical property ofthe optical recording medium is greatly affected by dust adhering to thesurface of the light transmittable substrate 2. On the other hand, ifthe light transmittable substrate 2 is too thick, it is difficult torecord data at high density by making the numerical aperture of therecording and reproducing optical system larger.

[0162] The light transmittable substrate 2 can be made thinner byadhering a light transmittable sheet made of a light transmittable resinonto the first dielectric layer 31 using any of various adhesives orsticking agents or directly coating a light transmittable resin layer onthe first dielectric layer 31, for example.

[0163] The support substrate 20 is provided for ensuring rigidity of theoptical recording medium. The support substrate 20 may have the samethickness as that of the light transmittable substrate 2 shown in FIG. 5and may be formed of the same material as that of the lighttransmittable substrate 2 shown in FIG. 5. The support substrate 20 maybe transparent or opaque. As shown in FIG. 6, grooves 2G can be formedby transferring grooves formed on the support substrate 20 onto therespective layers.

[0164] Other layers have the same configuration as that of thecorresponding layers of the optical recording medium shown in FIG. 5.

[0165] Explanation will next be made as to the structure of an opticalrecording apparatus to which the present invention can be applied.

[0166]FIG. 7 is a block diagram schematically showing a main portion ofan optical recording apparatus 50 for recording data in the opticalrecording media shown in FIGS. 5 and 6.

[0167] As shown in FIG. 7, the optical recording apparatus 50 includes aspindle motor 52 for rotating the optical recording medium 10, a head 53for projecting a recording beam onto the optical recording medium 10 andreceiving light reflected from the optical recording medium 10, acontroller 54 for controlling the operations of the spindle motor 52 andthe head 53, a laser drive circuit 55 for feeding a laser drive signalto the head 53 and a lens drive circuit 56 for feeding a lens drivesignal to the head 53.

[0168] Further, as shown in FIG. 7, the controller 54 includes a focusservo circuit 57, a tracking servo circuit 58 and a laser controlcircuit 59. When the focus servo circuit 57 is activated, a laser beamis focused on the recording surface of the optical recording medium 10being rotated and when the tracking servo circuit 58 is activated, thespot of the laser beam automatically follows a track of the opticalrecording medium 10. The focus servo circuit 57 and the tracking servocircuit 58 have automatic gain control capability for automaticallyfocus gain and automatic gain control capability for automaticallytracking gain, respectively. The laser control circuit 59 is adapted forgenerating a laser drive signal to be fed by the laser drive circuit 55based on information for setting recording conditions stored in theoptical recording medium 10 or the like.

[0169] It is not absolutely necessary for the focus servo circuit 57,the tracking servo circuit 58 and the laser control circuit 59 to beincorporated into the controller 54 but they may be providedindependently of the controller 54. Further, it is not absolutelynecessary for these circuits to be constituted as physical circuits andthe functions thereof may be performed in the controller 54 by software.

[0170] When data are to be recorded in the optical recording medium 10according to this embodiment using the thus constituted opticalrecording apparatus 50, as described above, information for settingrecording conditions stored in the optical recording medium 10 or thelike are read and write strategy is determined based on the thus readinformation for setting recording conditions.

[0171] Therefore, for example, when data are to be recorded in theoptical recording medium 10 at 2× linear recording velocity V_(L) by theoptical recording apparatus 50, the recording power and the bias powerare set to be PwL and PbiL, respectively, and the pulse width of the toppulse, the pulse width of the multi-pulse, the pulse width of the lastpulse and the pulse with of the cooling pulse are set to be TtopL, TmpL,TlpL and TclL, respectively. On the other hand, when data are to berecorded in the optical recording medium 10 at the 4× linear recordingvelocity V_(H) by the optical recording apparatus 50, the recordingpower and the bias power are set to be PwH and PbiH, respectively andthe pulse width of the top pulse, the pulse width of the multi-pulse,the pulse width of the last pulse and the pulse with of the coolingpulse are set to be TtopH, TmpH, TlpH and TclH, respectively.

[0172] Further, the bias power and the recording power at each of thelinear recording velocities V_(L) and V_(H) is set so as to satisfyPbiH/PbiL<1 and (PbiH/PwH)/(PbiL/PwL)<1 and the pulse widths arepreferably set so as to satisfy TclH/TclL<1, TmpH/TmpL≦1, TtopH/TtopL≦1and 1≦TlpH/TlpL. As a result, jitter of reproduced signals can bereduced when data are recorded both at the 2× linear recording velocityand the 4× linear recording velocity.

WORKING EXAMPLES Working Example 1

[0173] A sample of the optical recording disk shown in FIG. 6 wasfabricated in the following manner.

[0174] A disk-like polycarbonate plate having a diameter of 120 mm and athickness of 1.1 mm was used as a support substrate 20 and a raised anddepressed pattern was formed on the surface of the support substrate 20so as to form grooves and lands on a light transmittable substrate 2.

[0175] A reflective layer 5 was formed using the sputtering process inan atmosphere of Ar gas. As a target, Ag₉₈Pd₁Cu₁ was used. The thicknessof the reflective layer was 100 nm.

[0176] A second dielectric layer 32 was formed by the sputtering processusing a target of Al₂O₃ in the atmosphere of Ar gas. The thickness ofthe second dielectric layer was 20 nm.

[0177] A recording layer 4 was formed by the sputtering process using analloy target in the atmosphere of Ar gas. The composition (atomic ratio)of the recording layer was{(Sb_(0.82)Te_(0.18))_(0.93)M(In_(0.14)Ge_(0.86))_(0.07)}_(0.98)Tb_(0.02).The thickness of the recording layer was 12 nm.

[0178] A first dielectric layer 31 was formed by the sputtering processusing a target of ZnS—SiO2 (mole ratio 80:20) in the atmosphere of Argas. The thickness of the first dielectric layer was 130 nm.

[0179] Further, a light transmittable substrate 2 was formed by adheringa polycarbonate sheet having a thickness of 100 μm onto the surface ofthe first dielectric layer 31 via an adhesive layer of a solvent-typeultraviolet ray curable type acrylic resin having a thickness of 3 μm.

[0180] The recording layer of the thus fabricated optical recordingmedium was initialized (crystallized) using a bulk eraser.

[0181] Then, signals were recorded in the recording layer on the groovesusing a DDU1000 optical recording medium evaluation apparatusmanufactured by Pulstec Industrial Co., Ltd. under the followingconditions and recorded signals were reproduced.

[0182] Wavelength of laser beam: 405 nm

[0183] Numerical aperture of objective lens: 0.85

[0184] Recording Signal: (1.7) RLL modulation signal

[0185] The linear recording velocity V, pulse intensities Pw, Pbi, ratioof the pulse intensities Pw/Pbi, pulse widths Tcl, Tmp, Ttop and Tlpwere varied as shown in Table 1. Jitter of the reproduced signals isshown in Table 1. In Table 1, N is the relative linear recordingvelocity in relation to the linear recording velocity of 5.7 m/s andN=V/5.7. Pbo was fixed to be 0.1 mW and the sum of the width of anupward pulse and the width of a downward pulse in multi-pulses was 1 T.Therefore, the duty ratio was equal to Tmp. Further, in the recordingwaveforms shown in FIGS. 2 and 3, parameters other than Tmp were set soas to be the same as those of the recording waveform shown in FIG. 1.The shortest signal length n·Tw was 30.3 ns at the linear recordingvelocity of 5.7 m/s and it was 11.8 ns at the linear recording velocityof 14.6 m/s.

[0186] Jitter shown in Table 1 is clock jitter calculated as σ/Tw (%)where Tw is the width of a window and fluctuations σ is the fluctuationof the reproduced signals measured using a Time Interval Analyzermanufactured by Yokogawa Electric Corporation. The clock jitterindicates time fluctuation of a reproduced signal with respect to afrequency corresponding to the reference clock width (1T). Even if thetilt margin is considered, in other words, the optical recording disk istilted to increase jitter, there is no problem about signal quality ifthe clock jitter is equal to or lower than 10%, preferably equal to orlower than 9% when the optical recording disk is not tilted. TABLE 1 VPw Pbi Tcl Tmp Ttop Tlp Jitter Case # (m/s) N = V/5.7 (mW) (mW) Pbi/Pw(T) (T) (T) (T) (%) 101 5.7 1 4.5 2.0 0.444 1.00 0.40 0.40 0.50 8.3 10211.4 2 4.5 1.6 0.356 0.60 0.40 0.40 0.60 8.3 103 14.6 2.56 4.5 1.4 0.3110.40 0.35 0.40 0.60 8.5 104 14.6 2.56 4.5 1.4 0.311 1.10 0.35 0.40 0.609.8 105 14.6 2.56 4.5 1.4 0.311 0.40 0.50 0.40 0.60 9.7

[0187] In all cases shown in Table 1, PbiH/PbiL<1 and(PbiH/PwH)/(PbiL/PwL)<1 were satisfied at all linear recordingvelocities. As a result, jitter was equal to or lower than 10% in allcases.

[0188] Further, TclH/TclL<1 and TmpH/TmpL≦1, were satisfied in cases #101 to 103. As a result, jitter was equal to or lower than 9% in thesecases.

[0189] The jitter shown in Table 1 was measured after overwritingoperation was repeated ten times. Namely, it was possible to overwritedata at all linear recording velocities in this optical recording disksample.

Comparative Example 1

[0190] Data were recorded in and reproduced from the optical recordingdisk sample in the manner of Working Example 1 except that data wererecorded under the conditions shown in Table 2 and clock jitter wasmeasured. The results are shown in Table 2. In case # 201, all recordingconditions were the same as those in the case # 101. TABLE 2 V Pw PbiTcl Tmp Ttop Tlp Jitter Case # (m/s) N = V/5.7 (mW) (mW) Pbi/Pw (T) (T)(T) (T) (%) 201 5.7 1 4.5 2.0 0.444 1.00 0.40 0.40 0.50 8.3 202 14.62.56 4.5 2.2 0.489 0.40 0.35 0.40 0.60 13.2 203 14.6 2.56 3.0 1.4 0.4600.40 0.35 0.40 0.60 12.1

[0191] If case # 201 where jitter was within a tolerance range is takenas a reference case, PbiH/PbiL<1 was not satisfied between the referencecase and case # 202. Further, (PbiH/PwH)/(PbiL/PwL)<1 was not satisfiedbetween the reference case and cases # 202 and #203. As a result, jitterexceeded the tolerance range in cases # 202 and # 203.

[0192] According to the present invention, since the recording waveformis controlled in accordance with the linear recording velocity inmulti-pulse recording, jitter of the reproduced signal can be reducedeven when data are recorded at a wide range of linear recordingvelocities.

1. An optical recording method for recording data in an opticalrecording medium having a recording layer containing a phase changematerial at a plurality of linear recording velocities or a continuouslychanging linear recording velocity using a recording beam whoseintensity is modulated in accordance with a recording waveform, therecording waveform including a direct current section having anintensity of Pbi and a recording pulse section for forming a recordmark, the recording pulse section including at least three upwardpulses, among which an upward pulse between a first upward pulse and alast upward pulse has an intensity of Pw, Pbi and Pw being set so as tosatisfy PbiH/PbiL<1 and (PbiH/PwH)/(PbiL/PwL)<1 where PbiL and PwL arePbi and Pw when data are to be recorded at a linear recording velocityV_(L) selected from among the plurality of linear recording velocitiesor the continuously changing linear recording velocity and PbiH and PwHare Pbi and Pw when data are to be recorded at a linear recordingvelocity V_(H) which satisfies 1.1≦V_(H)/V_(L).
 2. An optical recordingmethod for recording data in an optical recording medium having arecording layer containing a phase change material at a linear recordingvelocity selected from among a plurality of linear recording velocitiesusing a recording beam whose intensity is modulated in accordance with arecording waveform, the recording waveform including a direct currentsection having an intensity of Pbi and a recording pulse section forforming a record mark, the recording pulse section including at leastthree upward pulses, among which an upward pulse between a first upwardpulse and a last upward pulse has an intensity of Pw, Pbi and Pw beingset so as to satisfy PbiH/PbiL<1 and (PbiH/PwH)/(PbiL/PwL)<1 where PbiLand PwL are Pbi and Pw when data are to be recorded at a linearrecording velocity V_(L) and PbiH and PwH are Pbi and Pw when data areto be recorded at a linear recording velocity V_(H) which satisfies1.1≦V_(H)/V_(L).
 3. An optical recording method for recording data in anoptical recording medium in accordance with claim 1, wherein therecording pulse section further includes a downward pulse having a widthof Tcl and following the last upward pulse and TclL and TclH are set soas to satisfy TclH/TclL<1 where TclL is Tcl when data are to be recordedat the linear recording velocity V_(L) and TclH is Tcl when data are tobe recorded at the linear recording velocity V_(H).
 4. An opticalrecording method for recording data in an optical recording medium inaccordance with claim 2, wherein the recording pulse section furtherincludes a downward pulse having a width of Tcl and following the lastupward pulse and TclL and TclH are set so as to satisfy TclH/TclL<1where TclL is Tcl when data are to be recorded at the linear recordingvelocity V_(L) and TclH is Tcl when data are to be recorded at thelinear recording velocity V_(H).
 5. An optical recording method forrecording data in an optical recording medium in accordance with claim1, wherein the upward pulse between the first upward pulse and the lastupward pulse has a width Tmp, and TmpL and TmpH are set so as to satisfyTmpH/TmpL≦1 where TmpL is Tmp when data are to be recorded at the linearrecording velocity V_(L) and TmpH is Tmp when data are to be recorded atthe linear recording velocity V_(H).
 6. An optical recording method forrecording data in an optical recording medium in accordance with claim2, wherein the upward pulse between the first upward pulse and the lastupward pulse has a width Tmp, and TmpL and TmpH are set so as to satisfyTmpH/TmpL≦1 where TmpL is Tmp when data are to be recorded at the linearrecording velocity V_(L) and TmpH is Tmp when data are to be recorded atthe linear recording velocity V_(H).
 7. An optical recording method forrecording data in an optical recording medium in accordance with claim1, wherein the first upward pulse has a width of Ttop, and TtopL andTtopH are set so as to satisfy TtopH/TtopL≦1 where TtopL is Ttop whendata are to be recorded at the linear recording velocity V_(L) and TtopHis Ttop when data are to be recorded at the linear recording velocityV_(H).
 8. An optical recording method for recording data in an opticalrecording medium in accordance with claim 2, wherein the first upwardpulse has a width of Ttop, and TtopL and TtopH are set so as to satisfyTtopH/TtopL≦1 where TtopL is Ttop when data are to be recorded at thelinear recording velocity V_(L) and TtopH is Ttop when data are to berecorded at the linear recording velocity V_(H).
 9. An optical recordingmethod for recording data in an optical recording medium in accordancewith claim 1, wherein the last upward pulse has a width of Tlp, and TlpLand TlpH are set so as to satisfy 1≦TlpH/TlpL where TlpL is Tlp whendata are to be recorded at the linear recording velocity V_(L) and TlpHis Tlp when data are to be recorded at the linear recording velocityV_(H).
 10. An optical recording method for recording data in an opticalrecording medium in accordance with claim 2, wherein the last upwardpulse has a width of Tlp, and TlpL and TlpH are set so as to satisfy1≦TlpH/TlpL where TlpL is Tlp when data are to be recorded at the linearrecording velocity V_(L) and TlpH is Tlp when data are to be recorded atthe linear recording velocity V_(H).
 11. An optical recording method forrecording data in an optical recording medium in accordance with claim1, wherein the intensities of the pulses and the widths of the pulsesused at the respective linear recording velocities V_(L) and V_(H) aredetermined by test recording.
 12. An optical recording method forrecording data in an optical recording medium in accordance with claim2, wherein the intensities of the pulses and the widths of the pulsesused at the respective linear recording velocities V_(L) and V_(H) aredetermined by test recording.
 13. An optical recording method forrecording data in an optical recording medium in accordance with claim1, wherein n·Tw≦20 ns is satisfied at a highest linear recordingvelocity where Tw is a width of a detection window and n·Tw is a signallength corresponding to a shortest record mark.
 14. An optical recordingmethod for recording data in an optical recording medium in accordancewith claim 2, wherein n·Tw≦20 ns is satisfied at a highest linearrecording velocity where Tw is a width of a detection window and n·Tw isa signal length corresponding to a shortest record mark.
 15. An opticalrecording method for recording data in an optical recording mediumhaving a recording layer containing a phase change material using arecording beam whose intensity is modulated in accordance with arecording waveform, the recording waveform including a direct currentsection having an intensity of Pbi and a recording pulse section forforming a record mark, the recording pulse section including at leastthree upward pulses, among which an upward pulse between a first upwardpulse and a last upward pulse has an intensity of Pw, a reference linearrecording velocity and recommended values of Pw and Pbi when data are tobe recorded at the reference linear recording velocity being given, andPbiL, which is Pbi when data are to be recorded at a linear recordingvelocity V_(L), and PbiH, which is Pbi when data are to be recorded at alinear recording velocity V_(H), being set so as to satisfy PbiH/PbiL<1and (PbiH/Pwh)/(PbiL/PwL)<1 where one of the linear recording velocityV_(L) and the linear recording velocity V_(H) is the reference linearrecording velocity and the other thereof is a linear recording velocityused for test recording, the linear recording velocity V_(L) and thelinear recording velocity V_(H) satisfy 1.1≦V_(H)/V_(L), therebydetermining Pw and Pbi used for the test recording or when data are tobe recorded at a linear recording velocity region including the linearrecording velocity for the test recording.
 16. An optical recordingmethod for recording data in an optical recording medium in accordancewith claim 15, wherein the recording pulse section further includes adownward pulse following the last upward pulse and having a width ofTcl, a recommended value of Tcl when data are to be recorded at thereference linear recording velocity is given, and Tcl for the testrecording is set so as to satisfy TclH/TclL<1 where TclL is Tcl whendata are to be recorded at the linear recording velocity V_(L) and TclHis Tcl when data are to be recorded at the linear recording velocityV_(H), thereby determining Tcl used for the test recording or when dataare to be recorded at a linear recording velocity region including thelinear recording velocity for the test recording.
 17. An opticalrecording method for recording data in an optical recording medium inaccordance with claim 15, wherein the upward pulse between the firstupward pulse and the last upward pulse has a width Tmp, a recommendedvalue of Tmp at the reference linear recording velocity is given, andTmp for the test recording is set so as to satisfy TmpH/TmpL≦1 whereTmpL is Tmp when data are to be recorded at the linear recordingvelocity V_(L) and TmpH is Tmp when data are to be recorded at thelinear recording velocity V_(H), thereby determining Tmp used for thetest recording or when data are to be recorded at a linear recordingvelocity region including the linear recording velocity for the testrecording.
 18. An optical recording method for recording data in anoptical recording medium in accordance with claim 15, wherein the firstpulse has a width Ttop, a recommended value of Ttop at the referencelinear recording velocity is given, and Ttop for the test recording isset so as to satisfy TtopH/TtopL≦1 where TtopL is Ttop when data are tobe recorded at the linear recording velocity V_(L) and TtopH is Ttopwhen data are to be recorded at the linear recording velocity V_(H),thereby determining Ttop used for the test recording or when data are tobe recorded at a linear recording velocity region including the linearrecording velocity for the test recording.
 19. An optical recordingmethod for recording data in an optical recording medium in accordancewith claim 15, wherein the last pulse has a width Tlp, a recommendedvalue of Tlp at the reference linear recording velocity is given, andTlp for the test recording is set so as to satisfy 1≦TlpH/TlpL whereTlpL is Tlp when data are to be recorded at the linear recordingvelocity V_(L) and TlpH is Tlp when data are to be recorded at thelinear recording velocity V_(H), thereby determining Tlp used for thetest recording or when data are to be recorded at a linear recordingvelocity region including the linear recording velocity for the testrecording.
 20. An optical recording method for recording data in anoptical recording medium in accordance with claim 15, wherein n·Tw≦20 nsis satisfied at a highest linear recording velocity where Tw is a widthof a detection window and n·Tw is a signal length corresponding to ashortest record mark.
 21. An optical recording apparatus for recordingdata in an optical recording medium having a recording layer containinga phase change material at a linear recording velocity selected fromamong a plurality of linear recording velocities using a recording beamwhose intensity is modulated in accordance with a recording waveform,the recording waveform including a direct current section having anintensity of Pbi and a recording pulse section for forming a recordmark, the recording pulse section including at least three upwardpulses, among which an upward pulse between a first upward pulse and alast upward pulse has an intensity of Pw, Pbi and Pw being set so as tosatisfy PbiH/PbiL<1 and (PbiH/PwH)/(PbiL/PwL)<1 where PbiL and PwL arePbi and Pw when data are to be recorded at a linear recording velocityV_(L) and PbiH and PwH are Pbi and Pw when data are to be recorded at alinear recording velocity V_(H) which satisfies 1.1≦V_(H)/V_(L), therecording pulse section further including a downward pulse having awidth of Tcl and following the last upward pulse and TclL and TclH beingset so as to satisfy TclH/TclL<1 where TclL is Tcl when data are to berecorded at the linear recording velocity V_(L) and TclH is Tcl whendata are to be recorded at the linear recording velocity V_(H), theoptical recording apparatus being constituted so as to store pulseintensities and pulse widths used at the linear recording velocity V_(L)and the linear recording velocity V_(H).
 22. An optical recordingapparatus for recording data in an optical recording medium inaccordance with claim 21, wherein the upward pulse between the firstupward pulse and the last upward pulse has a width Tmp, and TmpL andTmpH are set so as to satisfy TmpH/TmpL≦1 where TmpL is Tmp when dataare to be recorded at the linear recording velocity V_(L) and TmpH isTmp when data are to be recorded at the linear recording velocity V_(H).23. An optical recording apparatus for recording data in an opticalrecording medium in accordance with claim 21, wherein the first upwardpulse has a width of Ttop, and TtopL and TtopH are set so as to satisfyTtopH/TtopL≦1 where TtopL is Ttop when data are to be recorded at thelinear recording velocity V_(L) and TtopH is Ttop when data are to berecorded at the linear recording velocity V_(H).
 24. An opticalrecording apparatus for recording data in an optical recording medium inaccordance with claim 21, wherein the last upward pulse has a width ofTlp, and TlpL and TlpH are set so as to satisfy 1≦TlpH/TlpL where TlpLis Tlp when data are to be recorded at the linear recording velocityV_(L) and TlpH is Tlp when data are to be recorded at the linearrecording velocity V_(H).
 25. An optical recording apparatus forrecording data in an optical recording medium in accordance with claim21, which is constituted so as to store a plurality of pulse intensitiesand a plurality of pulse widths used at each of the linear recordingvelocity V_(L) and the linear recording velocity V_(H) and select apulse intensity and a pulse width used for recording data in the opticalrecording medium from the plurality of pulse intensities and theplurality of pulse widths by test recording of data in the opticalrecording medium.
 26. An optical recording apparatus for recording datain an optical recording medium in accordance with claim 22, which isconstituted so as to store a plurality of pulse intensities and aplurality of pulse widths used at each of the linear recording velocityV_(L) and the linear recording velocity V_(H) and select a pulseintensity and a pulse width used for recording data in the opticalrecording medium from the plurality of pulse intensities and theplurality of pulse widths by test recording of data in the opticalrecording medium.
 27. An optical recording apparatus for recording datain an optical recording medium in accordance with claim 23, which isconstituted so as to store a plurality of pulse intensities and aplurality of pulse widths used at each of the linear recording velocityV_(L) and the linear recording velocity V_(H) and select a pulseintensity and a pulse width used for recording data in the opticalrecording medium from the plurality of pulse intensities and theplurality of pulse widths by test recording of data in the opticalrecording medium.
 28. An optical recording apparatus for recording datain an optical recording medium in accordance with claim 24, which isconstituted so as to store a plurality of pulse intensities and aplurality of pulse widths used at each of the linear recording velocityV_(L) and the linear recording velocity V_(H) and select a pulseintensity and a pulse width used for recording data in the opticalrecording medium from the plurality of pulse intensities and theplurality of pulse widths by test recording of data in the opticalrecording medium.
 29. An optical recording apparatus for recording datain an optical recording medium in accordance with claim 21, whereinpulse intensities and pulse widths used at the linear recording velocityV_(L) and the linear recording velocity V_(H) are defined as functionsof the linear recording velocity V_(L) and the linear recording velocityV_(H), the optical recording apparatus being constituted so as to storethe functions.
 30. An optical recording apparatus for recording data inan optical recording medium in accordance with claim 22, wherein pulseintensities and pulse widths used at the linear recording velocity V_(L)and the linear recording velocity V_(H) are defined as functions of thelinear recording velocity V_(L) and the linear recording velocity V_(H),the optical recording apparatus being constituted so as to store thefunctions.
 31. An optical recording apparatus for recording data in anoptical recording medium in accordance with claim 23, wherein pulseintensities and pulse widths used at the linear recording velocity V_(L)and the linear recording velocity V_(H) are defined as functions of thelinear recording velocity V_(L) and the linear recording velocity V_(H),the optical recording apparatus being constituted so as to store thefunctions.
 32. An optical recording apparatus for recording data in anoptical recording medium in accordance with claim 24, wherein pulseintensities and pulse widths used at the linear recording velocity V_(L)and the linear recording velocity V_(H) are defined as functions of thelinear recording velocity V_(L) and the linear recording velocity V_(H),the optical recording apparatus being constituted so as to store thefunctions.
 33. An optical recording apparatus for recording data in anoptical recording medium in accordance with claim 21, wherein pulseintensities and pulse widths used at the linear recording velocity V_(L)and the linear recording velocity V_(H) are defined as functions of thelinear recording velocity V_(L) and the linear recording velocity V_(H),the optical recording apparatus being constituted so as to store aplurality of the functions for each of the linear recording velocityV_(L) and the linear recording velocity V_(H) and select functions usedfor recording data in the optical recording medium from the plurality ofthe functions by test recording of data in the optical recording medium.34. An optical recording apparatus for recording data in an opticalrecording medium in accordance with claim 22, wherein pulse intensitiesand pulse widths used at the linear recording velocity V_(L) and thelinear recording velocity V_(H) are defined as functions of the linearrecording velocity V_(L) and the linear recording velocity V_(H), theoptical recording apparatus being constituted so as to store a pluralityof the functions for each of the linear recording velocity V_(L) and thelinear recording velocity V_(H) and select functions used for recordingdata in the optical recording medium from the plurality of the functionsby test recording of data in the optical recording medium.
 35. Anoptical recording apparatus for recording data in an optical recordingmedium in accordance with claim 23, wherein pulse intensities and pulsewidths used at the linear recording velocity V_(L) and the linearrecording velocity V_(H) are defined as functions of the linearrecording velocity V_(L) and the linear recording velocity V_(H), theoptical recording apparatus being constituted so as to store a pluralityof the functions for each of the linear recording velocity V_(L) and thelinear recording velocity V_(H) and select functions used for recordingdata in the optical recording medium from the plurality of the functionsby test recording of data in the optical recording medium.
 36. Anoptical recording apparatus for recording data in an optical recordingmedium in accordance with claim 24, wherein pulse intensities and pulsewidths used at the linear recording velocity V_(L) and the linearrecording velocity V_(H) are defined as functions of the linearrecording velocity V_(L) and the linear recording velocity V_(H), theoptical recording apparatus being constituted so as to store a pluralityof the functions for each of the linear recording velocity V_(L) and thelinear recording velocity V_(H) and select functions used for recordingdata in the optical recording medium from the plurality of the functionsby test recording of data in the optical recording medium.
 37. Anoptical recording apparatus for recording data in an optical recordingmedium having a recording layer containing a phase change material usinga recording beam whose intensity is modulated in accordance with arecording waveform, the recording waveform including a direct currentsection having an intensity of Pbi and a recording pulse section forforming a record mark, the recording pulse section including at leastthree upward pulses, among which an upward pulse between a first upwardpulse and a last upward pulse has an intensity of Pw, a reference linearrecording velocity and recommended values of Pw and Pbi when data are tobe recorded at the reference linear recording velocity being given, andPbiL, which is Pbi when data are to be recorded at a linear recordingvelocity V_(L), and PbiH, which is Pbi when data are to be recorded at alinear recording velocity V_(H), being set so as to satisfy PbiH/PbiL<1and (PbiH/PwH)/(PbiL/PwL)<1 where one of the linear recording velocityV_(L) and the linear recording velocity V_(H) is the reference linearrecording velocity and the other thereof is a linear recording velocityused for test recording, the linear recording velocity V_(L) and thelinear recording velocity V_(H) satisfy 1.1≦V_(H)/V_(L), therebydetermining Pw and Pbi used for the test recording or when data are tobe recorded at a linear recording velocity region including the linearrecording velocity for the test recording, the recording section furtherincluding a downward pulse following the last upward pulse and having awidth of Tcl, a recommended value of Tcl when data are to be recorded atthe reference linear recording velocity being given, and Tcl for thetest recording being set so as to satisfy TclH/TclL<1 where TclL is Tclwhen data are to be recorded at the linear recording velocity V_(L) andTclH is Tcl when data are to be recorded at the linear recordingvelocity V_(H), thereby determining Tcl used for the test recording orwhen data are to be recorded at a linear recording velocity regionincluding the linear recording velocity for the test recording.
 38. Anoptical recording apparatus for recording data in an optical recordingmedium in accordance with claim 37, wherein the upward pulse between thefirst upward pulse and the last upward pulse has a width Tmp, arecommended value of Tmp at the reference linear recording velocity isgiven, and Tmp for the test recording is set so as to satisfyTmpH/TmpL≦1 where TmpL is Tmp when data are to be recorded at the linearrecording velocity V_(L) and TmpH is Tmp when data are to be recorded atthe linear recording velocity V_(H), thereby determining Tmp used forthe test recording or when data are to be recorded at a linear recordingvelocity region including the linear recording velocity for the testrecording.
 39. An optical recording apparatus for recording data in anoptical recording medium in accordance with claim 37, wherein the firstpulse has a width Ttop, a recommended value of Ttop at the referencelinear recording velocity is given, and Ttop for the test recording isset so as to satisfy TtopH/TtopL≦1 where TtopL is Ttop when data are tobe recorded at the linear recording velocity V_(L) and TtopH is Ttopwhen data are to be recorded at the linear recording velocity V_(H),thereby determining Ttop used for the test recording or when data are tobe recorded at a linear recording velocity region including the linearrecording velocity for the test recording.
 40. An optical recordingapparatus for recording data in an optical recording medium inaccordance with claim 37, wherein the last pulse has a width Tlp, arecommended value of Tlp at the reference linear recording velocity isgiven, and Tlp for the test recording is set so as to satisfy1≦TlpH/TlpL where TlpL is Tlp when data are to be recorded at the linearrecording velocity V_(L) and TlpH is Tlp when data are to be recorded atthe linear recording velocity V_(H), thereby determining Tlp used forthe test recording or when data are to be recorded at a linear recordingvelocity region including the linear recording velocity for the testrecording.
 41. An optical recording medium having a recording layercontaining a phase change material in which data are to be recorded at alinear recording velocity selected from among a plurality of linearrecording velocities using a recording beam whose intensity is modulatedin accordance with a recording waveform, the recording waveformincluding a direct current section having an intensity of Pbi and arecording pulse section for forming a record mark, the recording pulsesection including at least three upward pulses, among which an upwardpulse between a first upward pulse and a last upward pulse has anintensity of Pw, Pbi and Pw being set so as to satisfy PbiH/PbiL<1 and(PbiH/PwH)/(PbiL/PwL)<1 where PbiL and PwL are Pbi and Pw when data areto be recorded at a linear recording velocity V_(L) and PbiH and PwH arePbi and Pw when data are to be recorded at a linear recording velocityV_(H) which satisfies 1.1≦V_(H)/V_(L), the recording pulse sectionfurther including a downward pulse having a width of Tcl and followingthe last upward pulse and TclL and TclH being set so as to satisfyTclH/TclL<1 where TclL is Tcl when data are to be recorded at the linearrecording velocity V_(L) and TclH is Tcl when data are to be recorded atthe linear recording velocity V_(H), the optical recording medium beingconstituted so as to store pulse intensities and pulse widths used atthe linear recording velocity V_(L) and the linear recording velocityV_(H).
 42. An optical recording medium in accordance with claim 41,wherein the upward pulse between the first upward pulse and the lastupward pulse has a width Tmp, and TmpL and TmpH are set so as to satisfyTmpH/TmpL≦1 where TmpL is Tmp when data are to be recorded at the linearrecording velocity V_(L) and TmpH is Tmp when data are to be recorded atthe linear recording velocity V_(H).
 43. An optical recording medium inaccordance with claim 41, wherein the first upward pulse has a width ofTtop, and TtopL and TtopH are set so as to satisfy TtopH/TtopL≦1 whereTtopL is Ttop when data are to be recorded at the linear recordingvelocity V_(L) and TtopH is Ttop when data are to be recorded at thelinear recording velocity V_(H).
 44. An optical recording medium inaccordance with claim 41, wherein the last upward pulse has a width ofTlp, and TlpL and TlpH are set so as to satisfy 1≦TlpH/TlpL where TlpLis Tlp when data are to be recorded at the linear recording velocityV_(L) and TlpH is Tlp when data are to be recorded at the linearrecording velocity V_(H).
 45. An optical recording medium in accordancewith claim 41 which is constituted so as to store a plurality of pulseintensities and a plurality of pulse widths used at each of the linearrecording velocity V_(L) and the linear recording velocity V_(H) and sothat a pulse intensity and a pulse width used for recording data in theoptical recording medium are selected from among the plurality of pulseintensities and the plurality of pulse widths by test recording of datain the optical recording medium.
 46. An optical recording medium inaccordance with claim 42, which is constituted so as to store aplurality of pulse intensities and a plurality of pulse widths used ateach of the linear recording velocity V_(L) and the linear recordingvelocity V_(H) and so that a pulse intensity and a pulse width used forrecording data in the optical recording medium are selected from amongthe plurality of pulse intensities and the plurality of pulse widths bytest recording of data in the optical recording medium.
 47. An opticalrecording medium in accordance with claim 43 which is constituted so asto store a plurality of pulse intensities and a plurality of pulsewidths used at each of the linear recording velocity V_(L) and thelinear recording velocity V_(H) and so that a pulse intensity and apulse width used for recording data in the optical recording medium areselected from among the plurality of pulse intensities and the pluralityof pulse widths by test recording of data in the optical recordingmedium.
 48. An optical recording medium in accordance with claim 44which is constituted so as to store a plurality of pulse intensities anda plurality of pulse widths used at each of the linear recordingvelocity V_(L) and the linear recording velocity V_(H) and so that apulse intensity and a pulse width used for recording data in the opticalrecording medium are selected from among the plurality of pulseintensities and the plurality of pulse widths by test recording of datain the optical recording medium.
 49. An optical recording medium inaccordance with claim 41, wherein pulse intensities and pulse widthsused at the linear recording velocity V_(L) and the linear recordingvelocity V_(H) are defined as functions of the linear recording velocityV_(L) and the linear recording velocity V_(H), the optical recordingmedium being constituted so as to store the functions.
 50. An opticalrecording medium in accordance with claim 42, wherein pulse intensitiesand pulse widths used at the linear recording velocity V_(L) and thelinear recording velocity V_(H) are defined as functions of the linearrecording velocity V_(L) and the linear recording velocity V_(H), theoptical recording medium being constituted so as to store the functions.51. An optical recording medium in accordance with claim 43, whereinpulse intensities and pulse widths used at the linear recording velocityV_(L) and the linear recording velocity V_(H) are defined as functionsof the linear recording velocity V_(L) and the linear recording velocityV_(H), the optical recording medium being constituted so as to store thefunctions.
 52. An optical recording medium in accordance with claim 44,wherein pulse intensities and pulse widths used at the linear recordingvelocity V_(L) and the linear recording velocity V_(H) are defined asfunctions of the linear recording velocity V_(L) and the linearrecording velocity V_(H), the optical recording medium being constitutedso as to store the functions.
 53. An optical recording medium inaccordance with claim 41, wherein pulse intensities and pulse widthsused at the linear recording velocity V_(L) and the linear recordingvelocity V_(H) are defined as functions of the linear recording velocityV_(L) and the linear recording velocity V_(H), the optical recordingmedium being constituted so as to store a plurality of the functions foreach of the linear recording velocity V_(L) and the linear recordingvelocity V_(H) and so that functions used for recording data in theoptical recording medium are selected from among the plurality of thefunctions by test recording of data in the optical recording medium. 54.An optical recording medium in accordance with claim 42, wherein pulseintensities and pulse widths used at the linear recording velocity V_(L)and the linear recording velocity V_(H) are defined as functions of thelinear recording velocity V_(L) and the linear recording velocity V_(H),the optical recording medium being constituted so as to store aplurality of the functions for each of the linear recording velocityV_(L) and the linear recording velocity V_(H) and so that functions usedfor recording data in the optical recording medium are selected fromamong the plurality of the functions by test recording of data in theoptical recording medium.
 55. An optical recording medium in accordancewith claim 43, wherein pulse intensities and pulse widths used at thelinear recording velocity V_(L) and the linear recording velocity V_(H)are defined as functions of the linear recording velocity V_(L) and thelinear recording velocity V_(H), the optical recording medium beingconstituted so as to store a plurality of the functions for each of thelinear recording velocity V_(L) and the linear recording velocity V_(H)and so that functions used for recording data in the optical recordingmedium are selected from among the plurality of the functions by testrecording of data in the optical recording medium.
 56. An opticalrecording medium in accordance with claim 44, wherein pulse intensitiesand pulse widths used at the linear recording velocity V_(L) and thelinear recording velocity V_(H) are defined as functions of the linearrecording velocity V_(L) and the linear recording velocity V_(H), theoptical recording medium being constituted so as to store a plurality ofthe functions for each of the linear recording velocity V_(L) and thelinear recording velocity V_(H) and so that functions used for recordingdata in the optical recording medium are selected from among theplurality of the functions by test recording of data in the opticalrecording medium.
 57. An optical recording method for recording data inan optical recording medium having a recording layer containing a phasechange material by irradiating it with a recording beam whose intensityis modulated between a plurality of power levels including at least arecording power and a bias power, a recording power PwL and a bias powerPbiL when data are to be recorded at a first linear recording velocityand a recording power PwH and a bias power PbiH when data are to berecorded at a second linear recording velocity higher than the firstlinear recording velocity being set so as to satisfy PbiH/PbiL<1 and(PbiH/PwH)/(PbiL/PwL)<1.
 58. An optical recording method in accordancewith claim 57, wherein data are recorded so that the first linearrecording velocity V_(L) and the second linear recording velocity V_(H)satisfy 1.1≦V_(H)/V_(L)≦8.
 59. An optical recording method in accordancewith claim 57, wherein data are recorded so that a first linearrecording velocity V_(L) and a second linear recording velocity V_(H)satisfy 1.1≦V_(H)/V_(L)≦4.
 60. An optical recording method in accordancewith claim 57, wherein data are recorded so that a wavelength λ of therecording beam and a numerical aperture NA of an objective lens of arecording beam projecting optical system satisfy λ/NA≦680.
 61. Anoptical recording method in accordance with claim 60, wherein data arerecorded so that the wavelength λ of the recording beam and thenumerical aperture NA of the objective lens of the recording beamprojecting optical system satisfy 350≦λ/NA≦630.
 62. An optical recordingapparatus for recording data in an optical recording medium having arecording layer containing a phase change material by irradiating itwith a recording beam whose intensity is modulated between a pluralityof power levels including at least a recording power and a bias power, arecording power PwL and a bias power PbiL when data are to be recordedat a first linear recording velocity and a recording power PwH and abias power PbiH when data are to be recorded at a second linearrecording velocity higher than the first linear recording velocity beingset so as to satisfy PbiH/PbiL<1 and (PbiH/PwH)/(PbiL/PwL)<1.
 63. Anoptical recording medium having a recording layer containing a phasechange and in which data can be recorded by irradiating it with arecording beam whose intensity is modulated between a plurality of powerlevels including at least a recording power and a bias power, theoptical recording medium storing information for setting recordingconditions necessary for recording data under conditions where arecording power PwL and a bias power PbiL when data are to be recordedat a first linear recording velocity and a recording power PwH and abias power PbiH when data are to be recorded at a second linearrecording velocity higher than the first linear recording velocity areset so as to satisfy PbiH/PbiL<1 and (PbiH/PwH)/(PbiL/PwL)<1.